To enter safe mode restart your computer and tap the F8 Key, you should then get a startup menu which offers safe mode as an option.
If this fails then (Assuming you're using XP)
or other ROM menus interfere with the normal startup routine for Windows XP. Also using the safeboot option in MSCONFIG can occasionally result in an endless loop that could require replacing or rebuilding the boot.ini file. The following tool by noahdfear helps circumvent either issue.
If you are having difficulty accessing Safe Mode by tapping F8 during startup then please download and install SafebootCreator
. This will add a safemode option to your startup menu and give you 10 seconds to select this if required. Further information is available during the install.