Can not log into Windows with passwords

I have been running my Windows 7 Ultimate x64 system for over a year now with no problem. When I tried starting my system today I had this strange problem. I have 2 Admin accounts and one Std. user account set up. I usually use one of the Admin accounts I will call Admin-1. When I entered my password this morning to log in I get an "Invalid Password" message so I try all the normal things - is caps on, scroll, etc. I am sure I am typing it in correctly so I try logging in with the backup Admin account - Admin-2. I also get an Invalid Password error even though I KNOW I am putting in the correct PW. Finally I go in with the Std User account which does NOT have ANY password on it (luckily). Once in I go to User Management in the Control Panel and I get prompted for an Admin account and PW. I use Admin-1 account and the password which WORKS. I reset the PW on Admin-2 to a new password but when I try to switch users to the Admin-2 account I still get Invalid Password. Next I remove the password for the Admin-2 account then I am able to switch over to that account. I try changing the password on Admin-1 but when I try logging in I still get Invalid Password.

I do not want to remove the password on my primary Admin-1 account due to the warning message I get when doing so to the effect that I will lose all saved passwords and other goodies.

One other thing worth mentioning is that when the PC was last on my virus scanner found and 'treated' a slew or trojan/viruses in my temp Web directory. It looked like everything was honkey dory when I logged off. I also did another scan from the Admin-2 account this morning and nothing was found.

At this point it seems that I can not log into any account using the password for the account even though I know that the password is correct. Anyone have any ideas? Thanks.

I had a similar experience today. My password was changed 7 days ago. I know it and I have used it many times in the last 7 days as I always lock the OS when I leave my work area; a privacy thing at work. So it has worked for 6 days until today after lunch. I tried for half an hour with all kinds of combination of things, changing case, yanking my wireless keyboard. Doing Ctl Alt Del to get to the logon prompt. Flipping keyboard languages. Eventually I did get in-- to my surprise (nothing specail noted other than perseverance), then I poked around and locked it again to test. Took another 45 minutes to get in again. This time I went to the change password area and made a new password. So far so good.

I have had problems in this laptop with the login prompt. I had a p in a password and for some reason if I don't do C-A-D to get to the password prompt, the p triggers a control display dialog and fails the login.

My partner's theory is that the cpu is too hot and doing some kind of bit flips or flops. Not very kind. Anyhow, OK for now. Good luck to ya if you trip into this area.

Note to self: Maybe a good idea to make a backdoor login just to save some time in the future.