Wen i turn it on it is asking for password and i dont know it what do i do

Does it ask for a password Immediately when you turn it on? (CMOS password) or does windows boot up and then ask for both a username and password?

If the first, and you don't know what your password is, you can try clearing the CMOS by pulling the battery from the motherboard.

If it's a windows password, you or someone else created a password for it. Try just clicking OK, or enter Administrator as the username and leave password blank. Otherwise you may have to reset using ultimate boot CD.