I screwed up I need to go back to mac os x

[LxTxNx]

I guess I really screwed up... I got to Windows XP part of my MacBook pro I was trying to activate my xp account but it says my ID is invalid now I can't even go back to Mac OS X. Is there a button or something I can do on start up so that my Mbp starts in mac os x instead of so? HELP!!!!!

Btw I'm writting this from my iphone since I can't use my laptop!

 

[pknz]

Hold down the option key when you start up.

 

[LxTxNx]

you're ******* awsome! Thanks man!