Taken from a post off MS Social:
This means the file has been Tampered, Modified or has become Corrupt. Vista see this as an attack to bypass it's Licensing security.
To resolve the issue, you need to either repair file .
First try repairing Windows using System Restore:
1) Reboot Vista into Safe Mode
2) Click the 'Start' button
3) In the Start Search field, type: System Restore and hit "Enter" keyboard key
4) Select "Choose Different Restore Point", Put a check in the box that says "Show restore points older than 5 days", select the restore point that corresponds to the date Before you first noticed the issue.
5) Click the "Next" button.
6) Reboot back into Normal mode
7) Vista should no longer be in Reduced Functionality mode
If that doesn't work, we'll try doing a System Scan. The scan will look for bad Vista files and will attempt to repair them, if possible.
1) Login to Vista in Normal Mode (not safe mode)
2) Launch an Internet Browser
3) Type: %windir%\system32\ in the browser's address field
4) Scroll down till you find the file cmd.exe
5) Right-click the file and select 'Run as Administrator'
6) In the CMD window, type: sfc /scannow
7) Reboot twice and see if that resolves the issue.
If neither of these sets of steps resolves the issue, my only other suggestions would be either to contact Vista support at http://support.microsoft.com
or reinstall Vista.
Edited by diabillic, 13 September 2010 - 01:13 PM.