Sunday I had a problem after installing GHDL on my Windows 7 at work. Instead of appending to the PATH variable, it changed it to only contain GHDL. When I found out a couple of days later, I needed to figure out to get the PATH back. First I found out that the PATH is located in the registry under HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment\ and the registry data itself is located under %systemroot%\System32\Config\ in the SYSTEM file. So I needed a backup of the registration database file. I noticed that inside the Config folder there is a RegBack folder containing a backup of the registry from some days before. As I was working over remote desktop, and the file was locked, I needed a way for copying them. So by using ShadowCopy from Runtime, I made a copy of the system file, and by using regedit I loaded this file into a new key, and found my old path. Later I figured out that I might had been able to find the old path in the ControlSet00X instead of looking in CurrentControlSet, bud none the less I figured out a way to get it back.