How can i restore my laptop system? Windows Vista?

WITHOUT the pword. heres the reason. for some reason i cannot access my main account. so i only use my guest one. the pword, is right. but it always says 'user profile failed the logon' and point is, i dont care about loosing all my files. so i want to restore. but on my guest it asks for the administrative pword. And it doesn't work. the pword is correct, but it fails everything. please tell me, how to restore from my guest account. or is it like macintosh, where you press C, when you turn it on? thanks!