----

| Delaware                                                 |   | 75-2374449                         |
|----------------------------------------------------------|--------|------------------------------------|
| (State                or other jurisdiction              |   | (I.R.S.                Employer    |
| of                incorporation or organization)         |   | Identification                No.) |
|                                                     |   |                               |
| 6                Desta Drive, Suite 6500, Midland, Texas |   | 79705                              |
| (Address                of principal executive office)   |   | (Zip                Code)          |

| Indicate                by check mark whether registrant (1) has filed all reports required                to be                filed by Section 13 or 15(d) of the Securities Exchange Act of 1934                during                the preceding 12 months (or for such shorter period that the registrant                was required to file such reports), and (2) has been subject to such                filing requirements for the past 90 days:YesxNo ̈ |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Indicate                by check mark whether the registrant is a large accelerated filer,                an                accelerated filer, or a non-accelerated filer.  See definition                of “accelerated filer and large accelerated filer” in Rule 12b-2 of the                Exchange Act. |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Large                accelerated filer  ̈                                                                                                                                                                                                                                                                                        |   | Accelerated                filer  ̈ |   | Non-accelerated                filer  x |   |

| Indicate                by check mark whether the registrant is a shell company (as defined                in                Rule 12b-2 of the Exchange Act). |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  ̈                Yes                                                                                                                                     | x                No |

----

|                    | **Table                of Contents**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|-------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | **Page** |
|                    | Glossary                                                                                                                                                                                                     | 3        |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | **Part                I - FINANCIAL INFORMATION**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |     |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                1.  | Financial                Statements                                                                                                                                                                          | 5        |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | Balance                Sheets as of June 30, 2007 and December 31,                2006                                                                                                                       | 6        |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | Statements                of Operations for the three months and six months                ended June 30, 2007 and 2006                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     | 7        |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | Statements                of Cash flows for the six months ended June 30, 2007                and 2006                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | 8        |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                2.  | Management’s                Discussion and Analysis of Financial Condition                and Results of Operations                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   | 11       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                3.  | Quantitative                and Qualitative Disclosures About Market                Risk                                                                                                                     | 16       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                4.  | Controls                and                Procedures                                                                                                                                                        | 16       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | **Part                II – OTHER INFORMATION**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                1.  | Legal                Proceedings                                                                                                                                                                             | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                1A. | Risk                Factors                                                                                                                                                                                  | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                2.  | Unregistered                Sales of Equity Securities and Use of                Proceeds                                                                                                                    | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                3.  | Defaults                Upon Senior                Securities                                                                                                                                                | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                4.  | Submission                of Matter to a Vote of Security                Holders                                                                                                                             | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                5.  | Other                Information                                                                                                                                                                             | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
| Item                6.  | Exhibits                                                                                                                                                                                                     | 17       |
|                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |     |
|                    | Signatures                                                                                                                                                                                                   | 18       |

----

**Glossary      of Oil and Gas Terms**

*Bbl.      *

*BOE.  *

*Developmental      well. *

*Exploratory      well. *

*Farm-out      arrangement. *

*Field.      *

*Mcf.      *

*Net      Profits Interest.  *

*Oil.      *

*Overriding      royalty interest*

----

*Production      costs. *

*Proved      Area*

*Proved      developed oil and gas reserves. *

*Proved      properties*

*Proved      oil and gas reserves. *

*Proved      undeveloped reserves. *

*Reservoir.      *

*Royalty      interest. *

*Standardized      measure of discounted future net cash flows. *
* *

*Working      interest. *

*Workover.      *

----

**PART      I. - FINANCIAL INFORMATION**

**Item      1.                   Financial Statements**

----

**Southwest      Royalties Institutional Income Fund X-C,      L.P.**

**Balance      Sheets**

|                                                                   |   | **June                30,** |      |   | **December                31,** |   |
|------------------------------------------------------------------------|--------|-----------------------------|-----------|--------|---------------------------------|--------|
|                                                                   |   | **2007**                    |      |   | **2006**                        |   |
|                                                                   |   | **(unaudited)**             |      |   |                            |   |
| **Assets**                                                             |   |                        |      |   |                            |   |
|                                                                   |   |                        |      |   |                            |   |
| Current                assets:                                         |   |                        |      |   |                            |   |
| Cash                and cash                equivalents                |   | $                           | 44,672    |   |                            | $      | 29,985 |   |
| Receivable                from Managing General                Partner |   |                        | 41,285    |   |                            |   | 28,153 |   |
| New                Mexico income tax                deposits           |   |                        | 3,449     |   |                            |   | 3,047 |   |
| Total                current                assets                     |   |                        | 89,406    |   |                            |   | 61,185 |   |
|                                                                   |   |                        |      |   |                            |   |   |   |
| Oil                and gas properties - using the full-cost            |   |                        |      |   |                            |   |   |   |
| method                of                accounting                     |   |                        | 2,668,028 |   |                            |   | 2,668,028 |   |
| Less                accumulated                depreciation,           |   |                        |      |   |                            |   |   |   |
| depletion                and                amortization               |   |                        | 2,276,198 |   |                            |   | 2,255,562 |   |
| Net                oil and gas                properties               |   |                        | 391,830   |   |                            |   | 412,466 |   |
|                                                                   |   |                        |      |   |                            |   |   |   |
|                                                                   |   | $                           | 481,236   |   |                            | $      | 473,651 |   |
|                                                                   |   |                        |      |   |                            |   |   |   |
| **Liabilities                and Partners' Equity (Deficit)**          |   |                        |      |   |                            |   |   |   |
|                                                                   |   |                        |      |   |                            |   |   |   |
| Asset                retirement obligation                             |   | $                           | 986,930   |   |                            |   | 991,790 |   |
|                                                                   |   |                        |      |   |                            |   |   |   |
| Partners'                (deficit):                                    |   |                        |      |   |                            |   |   |   |
| General                partners                                        |   |                        | (88,345   | )      |                            |   | (91,471 | ) |
| Limited                partners                                        |   |                        | (417,349  | )      |                            |   | (426,668 | ) |
| Total                partners'                (deficit)                |   |                        | (505,694  | )      |                            |   | (518,139 | ) |
|                                                                   |   |                        |      |   |                            |   |   |   |
|                                                                   |   | $                           | 481,236   |   |                            | $      | 473,651 |   |

----

**Southwest      Royalties Institutional Income Fund X-C,      L.P.**

**Statements      of Operations**

**(unaudited)**

|                                                    |   | **Three                Months Ended** |    |   | **Six                Months Ended** |   |
|---------------------------------------------------------|--------|---------------------------------------|---------|--------|-------------------------------------|--------|
|                                                    |   | **June                30,**           |    |   | **June                30,**         |   |
|                                                    |   | **2007**                              |    |   | **2006**                            |   |   | **2007** |   |   | **2006** |   |
| **Revenues**                                            |   |                                  |    |   |                                |   |   |   |   |   |   |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |
| Income                from net profits interests        |   | $                                     | 119,051 |   |                                | $      | 166,540 |   |   | $ | 171,998 |   |   | $ | 261,732 |   |
| Interest                                                |   |                                  | 294     |   |                                |   | 384 |   |   |   | 478 |   |   |   | 864 |   |
| Gain                on sale of property and equipment   |   |                                  | -       |   |                                |   | - |   |   |   | - |   |   |   | 144,900 |   |
|                                                    |   |                                  | 119,345 |   |                                |   | 166,924 |   |   |   | 172,476 |   |   |   | 407,496 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| **Expenses**                                            |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Depreciation,                depletion and amortization |   |                                  | 12,248  |   |                                |   | - |   |   |   | 20,636 |   |   |   | - |   |
| Accretion                expense                        |   |                                  | 21,950  |   |                                |   | 12,157 |   |   |   | 44,246 |   |   |   | 24,039 |   |
| General                and administrative               |   |                                  | 16,932  |   |                                |   | 18,229 |   |   |   | 24,349 |   |   |   | 31,846 |   |
|                                                    |   |                                  | 51,130  |   |                                |   | 30,386 |   |   |   | 89,231 |   |   |   | 55,885 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Net                income                               |   | $                                     | 68,215  |   |                                | $      | 136,538 |   |   | $ | 83,245 |   |   | $ | 351,611 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Net                income allocated to:                 |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Managing                General                Partner  |   | $                                     | 7,242   |   |                                | $      | 12,289 |   |   | $ | 9,349 |   |   | $ | 31,645 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| General                Partner                          |   | $                                     | 804     |   |                                | $      | 1,365 |   |   | $ | 1,039 |   |   | $ | 3,516 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Limited                Partners                         |   | $                                     | 60,169  |   |                                | $      | 122,884 |   |   | $ | 72,857 |   |   | $ | 316,450 |   |
|                                                    |   |                                  |    |   |                                |   |   |   |   |   |   |   |   |   |   |   |
| Per                limited partner                unit  |   | $                                     | 10.06   |   |                                | $      | 20.54 |   |   | $ | 12.18 |   |   | $ | 52.89 |   |

----

**Southwest      Royalties Institutional Income Fund X-C,      L.P.**

**Statements      of Cash Flows**

**(unaudited)**

|                                                                                  |   | **Six                Months Ended** |    |
|---------------------------------------------------------------------------------------|--------|-------------------------------------|---------|
|                                                                                  |   | **June                30,**         |    |
|                                                                                  |   | **2007**                            |    |   | **2006** |   |
| Cash                flows from operating activities:                                  |   |                                |    |   |   |   |
|                                                                                  |   |                                |    |   |   |   |
| Cash                received from income from                net profits interests    |   | $                                   | 109,358 |   |   | $ | 278,620 |   |
| Cash                paid to                suppliers                                  |   |                                | (24,349 | ) |   |   | (31,846 | ) |
| Interest                received                                                      |   |                                | 478     |   |   |   | 864 |   |
| Net                cash provided by operating                activities               |   |                                | 85,487  |   |   |   | 247,638 |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Cash                flows used in financing activities:                               |   |                                |    |   |   |   |   |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Distributions                to                partners                               |   |                                | (70,800 | ) |   |   | (291,114 | ) |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Net                increase (decrease) in cash and cash equivalents                   |   |                                | 14,687  |   |   |   | (43,476 | ) |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Beginning                of                period                                     |   |                                | 29,985  |   |   |   | 51,969 |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| End                of period                                                          |   | $                                   | 44,672  |   |   | $ | 8,493 |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Reconciliation                of net income to net                                    |   |                                |    |   |   |   |   |   |
| cash                provided by operating                activities:                  |   |                                |    |   |   |   |   |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Net                income                                                             |   | $                                   | 83,245  |   |   | $ | 351,611 |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Adjustments                to reconcile net income to net                             |   |                                |    |   |   |   |   |   |
| cash                provided by operating                activities:                  |   |                                |    |   |   |   |   |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Depreciation,                depletion and                amortization                |   |                                | 20,636  |   |   |   | - |   |
| Settlement                of asset retirement                obligations              |   |                                | (49,106 | ) |   |   |   |   |
| for                plugged and abandoned                wells                         |   |                                |    |   |   |   |   |   |
| Gain                on sale of property and                equipment due to farm-out  |   |                                | -       |   |   |   | (144,900 | ) |
| Accretion                of asset retirement                obligation                |   |                                | 44,246  |   |   |   | 24,039 |   |
| (Increase)                decrease in                receivables                      |   |                                | (13,534 | ) |   |   | 16,888 |   |
| Net                cash provided by operating activities                              |   | $                                   | 85,487  |   |   | $ | 247,638 |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Noncash                investing and financing activities:                            |   |                                |    |   |   |   |   |   |
|                                                                                  |   |                                |    |   |   |   |   |   |
| Decrease                in oil and gas                properties – SFAS No. 143 |   | $                                   | -       |   |   | $ | 144,900 |   |

----

**SouthwestRoyalties      Institutional Income Fund X-C,      L.P.**

**(a      Delaware limited partnership)**

**Notes      to Financial Statements**

**1.                  Organization**

|                                                                              | Limited  |   | General  |
|-----------------------------------------------------------------------------------|----------|--------|----------|
|                                                                              | Partners |   | Partners |
| Interest                income on capital contributions                           | 100%     |   | -        |
| Oil                and gas sales                                                  | 90%      |   | 10%      |
| All                other revenues                                                 | 90%      |   | 10%      |
| Organization                and offering costs (1)                                | 100%     |   | -        |
| Syndication                costs                                                  | 100%     |   | -        |
| Amortization                of organization costs                                 | 100%     |   | -        |
| Property                acquisition costs                                         | 100%     |   | -        |
| Gain/loss                on property disposition                                  | 90%      |   | 10%      |
| Operating                and administrative costs (2)                             | 90%      |   | 10%      |
| Depreciation,                depletion and amortization of oil and gas properties | 100%     |   | -        |
| All                other costs                                                    | 90%      |   | 10%      |

|   | (1) | All                organization costs in excess of 3% of initial capital contributions                will                be paid by the Managing General Partner and will be treated as a                capital                contribution.  The Partnership paid the Managing General Partner                an amount equal to 3% of initial capital contributions for such                organization costs. |
|--------|-----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | (2) | Administrative                costs in any year, which exceed 2% of capital contributions shall                be paid                by the Managing General Partner and will be treated as a capital                contribution. |
|--------|-----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

**2.                  Summary of Significant Accounting Policies**

----

**Southwest      Royalties Institutional Income Fund X-C, L.P.**

**(a      Delaware limited partnership)**

**Notes      to Financial Statements**

**3.                  Abandonment Obligations**

|                                                                     |   | 2007   |    |   | 2006   |   |
|--------------------------------------------------------------------------|--------|--------|---------|--------|--------|--------|
| Beginning                of period                                       |   | $      | 991,790 |   |   | $      | 705,381 |   |
| Accretion                expense                                         |   |   | 44,246  |   |   |   | 24,039 |   |
| Reduction                due to farm-out                                 |   |   | -       |   |   |   | (144,900 | ) |
| Settlement                of obligations for plugged and abandoned wells |   |   | (49,106 | )      |   |   | - |   |
| End                of period                                             |   | $      | 986,930 |   |   | $      | 584,520 |   |

----

| **Item                2.** | **Management's                Discussion and Analysis of Financial Condition                and Results of                Operations** |
|----------------------------|----------------------------------------------------------------------------------------------------------------------------------------|

*General*

*Oil      and Gas Properties*

----

*Critical      Accounting Policies*

----

**Supplemental      Information**

|                                                     |   | **Three                Months Ended** |   |
|----------------------------------------------------------|--------|---------------------------------------|--------|
|                                                     |   | **June                30,**           |   |
|                                                     |   | **2007**                              |   |   | **2006** |   |
| Oil                production in barrels                 |   |                                  | 5,436  |   |   |   | 4,940 |   |
| Gas                production in mcf                     |   |                                  | 2,902  |   |   |   | 3,570 |   |
| Total                (BOE)                               |   |                                  | 5,920  |   |   |   | 5,535 |   |
| Average                price per barrel of oil           |   | $                                     | 59.60  |   |   | $ | 64.17 |   |
| Average                price per mcf of gas              |   | $                                     | 7.06   |   |   | $ | 5.95 |   |
| Partnership                distributions                 |   | $                                     | 45,800 |   |   | $ | 151,114 |   |
| Limited                partner distributions             |   | $                                     | 41,038 |   |   | $ | 135,768 |   |
| Per                unit distribution to limited partners |   | $                                     | 6.86   |   |   | $ | 22.69 |   |
| Number                of limited partner units           |   |                                  | 5,983  |   |   |   | 5,983 |   |

**Operating      Results**

**Income      from net profits**

**Expenses**

----

**Supplemental      Information**

|                                                     |   | **Six                Months Ended** |   |
|----------------------------------------------------------|--------|-------------------------------------|--------|
|                                                     |   | **June                30,**         |   |
|                                                     |   | **2007**                            |   |   | **2006** |   |
| Oil                production in barrels                 |   |                                | 9,474  |   |   |   | 9,341 |   |
| Gas                production in mcf                     |   |                                | 5,549  |   |   |   | 5,738 |   |
| Total                (BOE)                               |   |                                | 10,399 |   |   |   | 10,297 |   |
| Average                price per barrel of oil           |   | $                                   | 56.35  |   |   | $ | 60.94 |   |
| Average                price per mcf of gas              |   | $                                   | 6.87   |   |   | $ | 5.96 |   |
| Partnership                distributions                 |   | $                                   | 70,800 |   |   | $ | 291,114 |   |
| Limited                partner distributions             |   | $                                   | 63,538 |   |   | $ | 261,768 |   |
| Per                unit distribution to limited partners |   | $                                   | 10.62  |   |   | $ | 43.75 |   |
| Number                of limited partner units           |   |                                | 5,983  |   |   |   | 5,983 |   |

**Operating      Results**

**Income      from net profits**

**Gain      on Sale of Property and Equipment**

**Expenses**

**Liquidity      and Capital Resources**

----

**Texas      Margin Taxes**

**Recent      Accounting Pronouncements**

----

**Item      3.                   Quantitative and Qualitative Disclosures About Market      Risk**

**Item      4.                   Controls and Procedures**

**Internal      Control Over Financial Reporting**

----

**PART      II. - OTHER INFORMATION**

**Item      1.                   Legal Proceedings**

**Item      1A.                Risk Factors**

**Item      2.                   Unregistered Sales of Equity Securities and      Use of      Proceeds**

**Item      3.                   Defaults Upon Senior Securities**

**Item      4.                   Submission of Matter to a Vote of Security      Holders**

**Item      5.                   Other Information**

**Item      6.                   Exhibits**

|   | (a) | Exhibits: |
|--------|-----|-----------|

| 31.1 |   | Rule                13a-14(a)/15d-14(a) Certification                                                                                                                                                                                     |
|------|--------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 31.2 |   | Rule                13a-14(a)/15d-14(a) Certification                                                                                                                                                                                     |
| 32.1 |   | Certification                of Chief Executive Officer and Chief Financial Officer Pursuant to                18                U.S.C. Section 1350, as adopted Pursuant to Section 906 of the                Sarbanes-Oxley Act of 2002 |

----

**SIGNATURES**

|   | Southwest                Royalties Institutional Income Fund |
|--------|--------------------------------------------------------------|
|   | X-C,                L.P., a Delaware limited partnership     |
|   |                                                         |
| By:    | Southwest                Royalties, Inc., Managing           |
|   | General                Partner                               |
|   |                                                         |
|   |                                                         |
| By:    | /s/                L. Paul Latham                            |
|   | L.                Paul Latham                                |
|   | President                and Chief Executive Officer         |
|   |                                                         |
| Date:  | August                9, 2007                                |