Alas, deciding whether to upgrade your hardware isn't usually as straightforward. Although there's no foolproof formula that can tell you whether investing in add-on hardware is worth the cost, some basic math will help you decide if it makes sense to put money into an old computer. If you're still at a loss about what to do with a retired but functional Mac, consider donating it to a school or a nonprofit organization. Often you can deduct the computer's fair-market value on your tax return. Often, you'll have to add or update your old Mac's software to prepare the computer for a new role.
Some vendors offer limited versions of current applications that are compatible with old models.
Your System Software New Mac OS releases usually incorporate bug fixes and extra features, so you should consider upgrading to a later system software version than the one that originally shipped with your computer. Even the Macintosh 128K supports System 6, so you'll usually be able to choose from System 6 through 9. Consult the Apple Spec database to see which Mac OS versions your Mac supports. Next, find out which system software versions work with the programs you'll be running on your Mac. As a general rule, it's better to choose a recent Mac OS version, but keep in mind that newer software releases usually make more demands on RAM, hard drives, and processors.