what anti virus are you using?

Virgin Pc Guard.

Lol

Okay, here's what you should do:
Try using the game's built-in uninstaller. If that doesn't work, or it doesn't come with one or you can't find it, add/remove programs.
If you can't uninstall automatically, go to the game directory and delete ALL files--best to delete the entire Stardock folder, assuming you don't have any other games by them installed. Then go into your system registry (run-->regedit) and expand the LOCAL MACHINE and CURRENT USER folders, then go into the Software folders in both and delete the registry keys associated with Stardock, or just Sins if you have no other Stardock games installed.
That SHOULD be enough to clear any remnance of Sins from your system. Also, delete this folder:
C:\Documents and Settings\username\Local Settings\Application Data\Ironclad Games\Sins of a Solar Empire\

Restart.

Disable your virus scanner, and then install Sins again. I can say for a fact that Sins has no viruses or any kind in it, so you should be safe--assuming, of course, that you own a legal copy purchased via direct download or a retail store. You should now be able to play the game.