Bad Patch

I had to reinstall Vista on my computer (clean install) and ever since it's
given me problems. I started reinstalling programs and it had to restart and
when it did it wouldn't load Windows but instead gave me a page that said
that Windows was unable to start. I was able to fix it, and after it started
working again for a day or two (with me restarting it and turning it off,
etc.) it had the startup problem again, and again, and again. Everytime
something different fixes it. System restore usually worked, or Startup
Repair, but now its broken again and neither of those will fix it. When I
run Startup Repair and it goes through it and says that it was unable to fix
the problem, when I look at the details, it says that there's a "bad patch."
Does anyone know what that is and how to fix it? I could try reinstalling
Windows again but it's such a hassle plus I'm afraid I'll just have the same
problem again because I don't know what's causing it. Thank you!