Your registry can build up unnecessary entries over time from the adding/removing of programs and files. I would recommend CCleaner
if you want to use a good, free cleaner. If you use CCleaner, all you need to do is open the program, click the "issues" tab on the
left, click "Scan for Issues", and then click "Fix Selected Issues". It will ask you if you want to make a backup of the registry
before it fixes the issues. Make sure that you make this backup. I have never had anything go wrong when using CCleaner, but you
never know what could happen in the world of computers. After CCleaner is done fixing the selected issues, you are all set.
CCleaner has a few other good tools such as a tool to clear out temporary internet files, recycling bin, etc. This is a good first
step if you need to free up hard drive space. I would recommend cleaning up the registry every
time you run a spyware check. I try to do this once a month at the very least.
If you are looking for a software with a little more power, you can check out the
Lavasoft
Registry Tuner. This is a good tool from the company that makes ad-aware. This product does a good job of tuning up your
registry.