Following three simple steps now you can get rid of the pesky and sometimes buggy Windows Genuine Advantage (WGA) notifications:
1. Reboot Windows in safe mode (hold the f8 key while booting and you will get the option to boot in safe mode) and then:
2. Open Registry Editor (regedit.exe) and search for wgalogon folder and delete it. You should backup up the registry beforehand, in case somethiong goes wrong.
3. In your windows directory search for files wga* and delete them.
You are done!
Now reboot back normally and continue your work. Windows Genuine Advantage will not bother you anymore.
Warning: Use at your own risk. Backup everything before you do.