To get into safe mode, keep pressing the F8 button on the keyboard right after the computer logo dissapears, then scroll up to last configured that worked.
Try that first , Then try the following :
-edit-
Go to my computer and right click it / then properties / then click the advanced tab / then uncheck the box where it say's reboot. Then reboot.
By the way, these are instructions if your running XP as your OS.