Quick question about vista

[Jesus Is Here]

I have recently installed vista on my comp, i upgraded from xp media edtion.

Now when i turn my comp on it gives me a option to ethier run vista or XP, when i go to pick XP it asks for a admin password, i never put a password on so i just hit enter leave it blank and it says wrong Password...

IM CERTAIN that i never put a password on, i just want to use XP again, vista sucks(no offense)

so really i wanan know how i can downgrade from vista back to my XP...

if anyone can help id be very VERY happpy, i hate vista i jsut want xp back