You can edit the msdos.sys file in the root to force the menu, but this is only neccessary if you are running Win95. With Win98 and ME, you can go to Start, Run and type in msconfig - this will bring up a configuration program, in the lower right corner will be a button marked Advanced, click on that one and check the menu option for Enable Boot Menu. Close the program and reboot when prompted, this should force the menu up where you can choose Safe Mode. If you have Win2000 or XP, you hit F6 while in the beginning of the boot routine, but safe mode is very cyriptic under these op sys.
Hope this helps,
Vickie