When powering on the computer, watch what happens. First
you should see some messages on a black screen maybe a
logo from the manufacturer (Sony, Dell, etc.). Then, the
Windows screen comes up and the operating system begins to
load. When the manufacturer logo disappears from the
screen you should tap-tap-tap the F8 key about once per
second, BEFORE the Windows screen comes on and take the
SAFE mode option from the menu.
Alternately you can (from Windows) go to Start, Run and
type MSCONFIG and hit OK. Go to the Boot.ini tab and put
a check mark next to /SAFEBOOT then hit Apply, OK and
reboot as directed. When you get to SAFE mode, run
MSCONFIG again (when you're finished doing what you're
doing) and turn the /SAFEBOOT switch off (uncheck it), hit
Apply, OK, then reboot.
Good Luck !