Use System Restore...
Always create a restore point using System Restore when installing or deleting software. You'll find the applet in Accessories > System Tools > System Restore.
|...unless you're infected|
If your computer has been infected by viruses or spyware, System Restore may actually preserve these Net nasties. Temporarily disable System Restore and perform a full system scan. After you've cleaned your PC, delete old restore points and start fresh.