Can you run it in safe mode? If you can, and are able to, run the command prompt sfc /scannow and see if that finds the issue. If not, I found this just googling for a bit, so maybe it will help:
Start Menu / All Programs / Accessories, right click on Command Prompt and pick/select 'Run As admistartor'.
At the command prompt enter: slmgr -upk
Now try phone activation:
How to activate Windows 7 or Vista manually (activate by phone)
1) Click Start, and in the Search box type: slui.exe 4
2) Next press the 'ENTER' key
3) Select your 'Country' from the list.
4) Choose the 'Phone Activation' option.
5) Stay on the phone (do not select/press any options) and wait for a person to help you with activation.
Also:
How to resolve common activation problems
(you need an account to see links)
Windows Activation Video
(you need an account to see links)
This video will show you: - How to activate Windows - Where to find your product key
How to use your product key - How to get support for product activation
How to Activate Windows 7 by Phone
(you need an account to see links)
(you need an account to see links)
Microsoft Activation Centers Worldwide Telephone Numbers:
(you need an account to see links)
(This site is for Volume License Activation but if you call they will help you)
The phone number you called does not work:
Microsoft Wordwide contacts:
(you need an account to see links)
@
(you need an account to see links)