I locked myself out in Windows 7

today, I had to re-enter the domain. While I was trying to re-join the domain I encountered strange errors and find myself in a situation where:

- I cannot run as administrator--nothing!
- the default administrator account was disabled
- The username / password which I typed in when installing windows 7 does not seemed to help me, has no priviliges/permissions to run net user commands

I was completely stuck!

so here is what I did:

• shut down the computer, restart and press F8 to select startup options. select safe mode: it will login as administrator
• Run the command prompt as administrator (by right click-run as administrator)
• I typed net user administrator /active:yes but it complained like "the password does not meet with policy requirements" so
• type net user administrator Password  (password should be the password you desire)
• then net user administrator /active:yes 

Bravo! now after a normal startup enter with your administrator account and do anything you want!