We cannot assist with password related issues at Tom's Hardware. We have no way of knowing whether or not the product is yours or somebody else's, stolen or even restricted by work regulations. Unfortunately, if you've bought the item without knowing passwords or the password has somehow been lost, you'll have to seek assistance elsewhere. You can start here:
http://windows.microsoft.com/en-us/windows7/solutions-to-common-problems-with-logging-on-to-windows
If it's not a log in issue, and you are simply trying to do something on the unit and it won't let you complete the action, you'll need to either go into User accounts in control panel and enable your current account as an administrator or disable UAC user account control to...