Booting Windows into Safe Mode
Safe Mode is an operating mode of Microsoft Windows that prevents many un-necessary applications (and viruses) from running when Windows starts up. There are obvious signs that you're in Safe Mode when Windows loads like text in all four corners of the desktop indicating "Safe Mode" and your normal desktop background removed (just during Safe Mode).
There are several different Safe "Modes" like the standard Safe Mode, Safe Mode with Networking, Safe Mode with Command Prompt, etc. The most commonly used mode is Safe Mode with Networking because it allows Internet access from Safe Mode (important for most virus removal).
Using the arrow keys on your keyboard, select the option Safe Mode with Networking and press the Enter key. Depending on your version of Windows, you may or may not get a warning/notice pop-up screen that asks if you "really want to do this", if you do, click Yes.
NOTE: Some keyboards use the function keys (F1 through F12) for alternate functions so you may have to toggle an F Lock key to enable the default key functionality. Also, some computers, like some Sony models, use F8 for their own purposes so you have a very small window of time to tap the key to enter Safe Mode in some cases, this will be a trial and error process.
Here is a write-up on Safe Mode from Microsoft for more details:
http://support.microsoft.com/kb/315222