Windows is well-known for having driver and .dll conflicts, as well as all sorts of software that causes problems with your computer. Luckily there's a System restore feature that can return your computer back to a known working configuration, as long as you've created a restore point.
Note that some software installations will create restore points automatically, but you should run it manually before installing any questionable applications. (Or better yet, don't install questionable applications!)
Creating a Restore Point Manually
To create a Restore Point click on Start \ programs\ Accessories \ System Tools \ System Restore, and you'll be given a wizard screen.
Click on "Create a restore point" and then click the Next button. You'll be brought to a screen where you can type in a description for your restore point. Use something memorable if possible.
Once your restore point is created (which might take a while), you will get a confirmation screen.
All done creating the restore point!