Just start hitting F8 straight from BIOS, that always works. If you want to get to DOS in XP I'm not sure though. I have HOME :(, and the only way to get to DOS is to boot from the CD and select .... uhm, recovery mode or something along those lines. Not really sure what it's called, but I do know it takes ages to load all kinds of drivers you'll never use in DOS, and that the final state is something that may have you fooled it's DOS, but not quite ;)