2. Back up files, clean the hard drive

Even with extra memory, Windows computers are notorious for becoming slower and buggier over time. Simply wiping the hard drive and reinstalling everything from scratch often leads to a dramatic improvement in performance. It's a time-consuming but cheap way to speed up an older computer.

The fastest solution is an external hard drive that pops into a USB port and can back up your files in a matter of hours. A 500-gigabyte external drive can be found for around $125 -- more than you want to spend, perhaps. But if you can't afford to back up your computer files, you can't afford a computer.