So I got this new computer, a Dell XPS 8100, and it runs fine. I spend a week getting every setting fine-tuned and today it tells me my Windows 7 (Home, 64bit) isn't genuine. I tried reentering the key through the command prompt ( slmgr.vbs -ipk [key] ) and it gave me an error. I tried again. It works. So I try activating the new product key, ( slmgr.vbs -ato ) and it fails. So I use the legit check from Windows. It works! and then ten minutes later it says my Windows is invalid again.

I think it'd almost be easier to pirate it at this point. Any ideas though?

I think you should go to your relater and check is your windows legal or not.

Pirate it. :) I had the same trouble after I installed (Custom) Windows 7 upgrade that I bought, I called Microsoft and Digital River (Microsoft's sales vendor for the download)and both of them told me the error was my fault and I used the number wrong.
I reinstalled Windows and it gave me the validation error twice. I found a pirate crack and I am on talking to you. They are terrible I may go to Linix.