**Exhibit 31.1**

**CERTIFICATION PURSUANT TO 17 CFR 240.13a-14(a)**

**PROMULGATED UNDER SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002**

I, Mikel H. Williams, certify that: 

1. Ihave reviewed this quarterly report on Form 10-Q for the quarter ended September 30, 2007 of DDi Corp.; 

2. Based on my knowledge, thisreport does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the periodcovered by this report; 

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairlypresent in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report; 

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internalcontrol over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have: 

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared; 

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability offinancial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles; 

(c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the endof the period covered by this report based on such evaluation; and 

(d) Disclosed in this report any change in theregistrant’s internal control over financial reporting that occurred during the registrant’s third quarter ended September 30, 2007 that has materially affected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting; and 

5. The registrant’s other certifying officer and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions): 

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which arereasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and 

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting. 

 

Date: November 7, 2007