Reset PC, Install as Admin (Right Click, Run as Administrator)
Personally I prefer to mix them up a bit and create my own versions, Newer apaches with php 5+ with the old mysql and a few other things.
You might want to try the old Wamp 0.5.1 (Can provide link if needed)
Other than that, go to start menu, type services.msc Look for Apache, Stop the service, Disable it, Reinstall it. If that don't fix your Issue, PM Me I'll try and provide Live support via MSN/TeamViewer