Hmph. If you need DOS compatability, forget using Windows - Microsoft needs to be encouraged to just walk away from it. Instead, use something like
Dosbox. It's safer and I haven't found a DOS game yet it doesn't do (though you need a VERY powerful machine). This way, if it crashes, you just close the window... it's in its own box and can't affect the rest of the OS.
Also, scan your system with Adaware and Spykiller - something may have come in and is screwing with you.