Alright, I've had similar situations with other applications and here's how I fixed it. First, copy all of your workspaces to some other directory. Then uninstall Visual C++. There's usually quite a few files that aren't deleted for some reason when you uninstall, so manually delete these, then defrag your hard drive and reinstall. If this doesn't fix it, it can't be a problem with VC++ so it's probably a Windows issue. If this is the case, you should at least try doing a system restore. Go to Programs, Accessories, System Tools, System Restore and select a date where you know the program worked (assuming that it worked at one point in the past). There's no guarentee this will fix it, and every program that you've installed since the date you select may need to be reinstalled, but it's worth a try before you have to reformat. If all else fails, try reinstalling Windows, and if that doesn't fix it, I can't think of anything other than reformating.
Hope this helps. Let me know how it turns out.