I just recently re installed the OS for my ibook and i forgot the user name and password i used. What can i do?
Boot from the install disk and use the password reset utility. Make a note of it when you set the new one this time somewhere.
Boot from the OS X disk as if you were going to do a reinstall. When it gets past the language selection screen there should be a menu called Utilities or something on top (forget what its called). There you should find a bunch of nifty little thingers, Disk Utility, Terminal and the Password reset one. Use that to reset your password and there you go.
Restart with the disk in the drive and hold down the C key while it restarts. This will force it to start up from the CD.
Turn it off by holding down the power button. Then restart it, simultaneously feeding in the disc, and holding down the Alt key. This should, after a few moments, give you a choice of Startup Disks. Select the OSX DVD.