It's one of 2 things: RAM problem or HD problem. Bad sectors on the hard drive could prevent certain things from loading, or certain items can't load to bad areas in RAM.
You could reinstall if it's a HD problem, as most likely the items will be installed to different sectors of the hard drive, and it may work. If it's ram, it'll do the same thing, and it may not even reinstall, giving you a blue screen during the reinstall process.
Download an item called Hirens Boot Disc, burn it to CD, and run Memtest86+ and Test Hard Disk Drive. Should identify the problem from there.