1) Uninstall sins and impulse and most important restart comp. If you want to continue your save games you will need to install from CDs. I'm assuming you did a CD installation.
2) If you updated, old save games don't work. You have to start new game.
I've never used a restore point....so I dunno how exactly does that work. I either uninstall or wipe my harddrive clean.
Check add/remove programs from control panel. If sins is there...than uninstall it and re-install directly from web via impulse (latest version with AI improvements) or CD (if you want to continue to used old save games).
