Ibook g4 password wont accept

Hello,

My ibook was having some issues earlier today, freezing up, being unresponsive - the task bar at the bottom would not work, couldnt put anything in the trash bin, hugely reduced speed - a number of things. I held down the power button to force a restart because it would not restart on it's own, I was worried it was a virus or something.

When it booted back up, it requested my password, which it did not accept. I am fairly certain I know the password and have tried any number of iterations in place of it, to no success. I do not have a Mac OSX disc, as this computer was a hand-me-down, so that particular avenue seems unlikely.

Any thoughts? The only other time the computer has had any issues, a friend sequestered a bit of my HD off as a seperate...I dont know, but a portion of my computer is still available, albeit at greatly reduced functionality. I can check certain email accounts, there are things I cant access online, it's all very confusing. I'm mostly just worried about my files on the HD.

Any assistance would be greatly appreciated.