Resolving Vista issue "An unauthorised change was made to Windows"
-
I have spent a lot of time in figuring out this issue so I thought it better to share my experience with others. I had Debugging Tools for Windows (x64) installed on my vista 64 and was doing some debugging, during my work I had to restart the system and when I tried to log on after restart it showed me a pop up dialog stating something like "An unauthorised change was made to Windows" "Windows has discovered a change that will result in limited Windows functionality. Use the link below to find out more." giving two options either to close dialog (which used to take me back to logon screen) and to visit the mentioned link. It took me some time to figure out that I accidently turned on the system wide pageheap using gflags, and though this feature is provided by Microsoft itself in its debugging tools but still it doesn't work with Vista and causes it to prevent user from logging in. Another interesting thing is that if you visit the link then at some place it will start validating if your OS is genuine and it will report you in the end that your windows is not genuine and you won't be able to do anything from there. To solve the issue restart the system in safe mode and clear the system wide pageheap from gflags and restart it normally, it will then allow you to log in. :)