Hi everyone!
I need some help for my windows xp, when I want to log on, on one of my account (I have four including the guest one) it just keep saying the password is incorrect. I can still use the guest one, but not for many thing. And I didn't forgot my password! I use it 2 weeks ago without any problems, untill now.

Thanks!

Is this account you can no longer log into a local machine administrator ???

If so, I would think that somebody was logged onto it and changed the password.

Otherwise the only other possibility is a corrupt user account.

Can you logon to any other local user account that has admin previlages ???

If so then you will want to archive/grab any data files and then delete this account and create a new one and restore your documents.

No i can't use any admministrator account, just the guest one,

OK, got you.

I've heard that a Password Reset Boot Disk will work, although I've never had to use one myself, yet.

Google Search

Right thank i get to the point after the reboot with CD, when i have to type in yes. Well thats not easy because my keybord just not working untill the xp started. I am using a wireless Logitech Ex 100. Now if u have any ideas what to do please tell me!

Sorry, but you need to get youself a cheap PS2 keyboard to get into the BIOS and also to do any special F5/F8 key combos.

Always remember to have a cheap keyboard like this for testing.

here is the methods I know.

The first thing which you check if you forget login password. When we install Windows, it automatically creates an account "Administrator" and sets its password to blank. So if you have forget Your user account password then try this:
Start system and when you See Windows Welcome screen / Login screen, press ctrl+alt+del keys Twice and it'll show Classic Login box. Now type "Administrator" (without quotes) in Username and leave Password field blank. Now press Enter and you should be able to log in Windows.
Now you can reset your account password from "Control Panel -> User Accounts".
Same thing can be done using Safe Mode. In Safe Mode Windows will show this in-built Administrator account in Login screen.

Windows XP and further versions also provide another method to recover forgotten Password by using "Reset Disk". If you created a Password Reset Disk in Past, you can use that disk to reset the password. To know more about It, please visit http://www.resetwindowspassword.com/