Safe Mode is a way for Windows to boot with only the minimum necessary system files. This is a great tool for troubleshooting. It also makes scanning for viruses and spyware much more effective. The drawbacks to Safe Mode are the fact that the video display is not very good and some programs won't run while in Safe Mode.

To enter Safe Mode, tap the F8 key when first booting the PC. You will often get a boot menu where you can select Safe Mode from the options.