If any thing simple errors (forexample any blue screen erors) that is appropreate way to fix the problem; boot the windows in safe mode. and return to user mode.Thats immportant a PC user must know how to boot the PC in safe mode.
following tips may help ful to know.
*Turn the computer on or Restart the computer
*Start tapping the F8 key. The Windows Advanced Boot Options Menu appears. If you begin tapping the F8 key too soon, some computers display a "keyboard error" message. To resolve this, restart the computer and try again.
*Ensure that the Safe mode option is selected (the top option)
Press Enter. The computer then begins to start in Safe mode.
*When you are finished with troubleshooting, close all programs and restart the computer as you normally would.
Thats almost same in vista nad Xp.
