You don't need to
downgrade the OS. We run Vista Home Basic on our laptop and Vista Home Premium on my wife's computer. FPSC runs perfect on both of them.
When you are installing applications or the updates, you right-click and hold on the file, then select "Run As Administrator". It will install properly. Another tip is not to install into places like Program Files, particularly if you need to copy files to the location. That's one of the reasons we specified a specific location. As a developer for RPG Mod, I have to copy files to my RPG Mod folder and it is a pain to do so if it's installed in the Program Files location. You can copy if you have to, but to the average user, they will be told it can't be done and they get frustrated.
We installed our FPSC in the C:\The Game Creators\FPS Creator folder and have never had one issue. You can always try that.
- BlackFox

RPG Mod- Create a world full of adventure