Using Chnptw On An Un-need Password On An Administrator Account?

I have a windows 7 ultimate edition 32 bit and linux mint 11 Katya on dual boot, I forgot my password for the only user account on windows 7 and that account was an administrator, unfortunately, i never created the password reset disk, after trying for a day or 2 to figure the password out, i started using mint to my advantage, i downloaded and installed a tool called "Chntpw", it's supposed to remove the password entirely or change it and it's able to unlock locked accounts like the guest account, i used the following command after changing the directory to my Windows/System32/config:

Sudo chntpw -u <myusername> sam

for some reason my SAM file is in lower case letters, anyways after using that to remove the password on my account, it says it was successful and i saved it and even checked it again and it says that it no longer requires a password, but when i rebooted my pc into windows 7, it still asked for a password, and after trying to a few other things like unlocking the administrator and guest accounts, 3 things happened: my account's profile picture changed, the password hint i typed disappeared and switch user option appeared, i tried using it but it for administrator it requires a password even though chntpw says it doesn't, and for the guest account it says that the method i'm using to log in isn't allowed.so i'm basically stuck out of my windows 7, and i'm doing my best to avoid a reinstall cuz my windows installation is 2.5 years old and it's working real fine and has alot programs, personal data and drivers installed.