Should I get a registry cleaner or a program to "speed up" my PC?

Be skeptical of "cleaning" applications. Applications that make vague claims about improving your PC's performance and clearing out its clutter (Registry cleaners, I'm looking at you) will generally do more harm than good (if they do anything at all). To clean up your system, simply run Disk Cleanup (to reach it, select Start Menu, All Programs, Accessories, System Tools); it comes with every Windows installation and it won't mess up your PC.