Password sabotage

Hello Smart Ones,

I'm the not so Smart One with a not so nice ex-roommate. She sabotaged my computer by changing the administrator password on my 3 year old Toshiba Satellite laptop. I have read loads of forums on how to recover one's administrator password, but none of them work - I don't have a password recovery disk, starting in safe mode and going to Administrator does not work - nothing helpful on the web has enabled me to figure out the new password. And unfortunately, my computer did not come with any disks, so I don't have a recovery disk, a Windows 7 disk, etc. And being not so smart myself, I did not create a password recovery disk.

I bought this laptop to use on vacation, and I haven't used it myself for a year. I let the ex-roomie use it when she was here. She is long gone, and I'm going on vacation in 6 days and just discovered that I can't log in. I need to take the laptop with me. So my question is this - if I buy a new Windows 7 disk, would I be able to install it on the laptop and overwrite the old Windows 7 program and make my computer work again? I'm willing to buy what I need to get this machine working, but I don't have a lot of $$ to throw at a computer that I use 5 days a year.

Any suggestions on how I can get the laptop working before I leave on vacation?

PLEASE HELP!!!!

Thanks in advance for helping me get this thing working again.