Need help with MacBook

ok so my friend has an issue with her macbook, i told her, her problem, its a mac, but that did not suffice, when ever she goes to log into her account
name and password are correct, starts to log in then poof back to the log in screen, im a strict PC user, and personally would love to set fire to Apples all over the world, but thats just my opinion, I would like to know if there is a way to resolve this, or how to put a copy of OSXSL onto a Flash drive using Win Vista, i know Fail there aswell, but its what i got since my last mobo fried. . . any useful information will be greatly appreciated,

She should have her installation discs for her MacBook.

Try booting from the disk and repairing permissions, if all else fails, perform an archive and install. This preserves the user accounts, applications and data, while replacing the system folder.

Thanks to "theappleblog.com/category/how-to/"
# Reboot
# Hold apple + s down after you hear the chime.
# When you get text prompt enter in these terminal commands to create a brand new admin account (hitting return after each line):

* mount -uw /
* rm /var/db/.AppleSetupDone
* shutdown -h now

# After rebooting you should have a brand new admin account.

Just Follow these steps... After you create a new account, Change/ Remove the old Password.