Re: Computer won't POST after dissembling it...
it could be the gpu as I mentioned it before, or it could be the PSU as slay suggested before, or it could be the motherboard as MoM suggested before. We're giving you plenty of ideas as well as ideas of how to test for it, so instead of saying well it could be this or it isn't this try some stuff out and get back to us on what works and what doesn't. Retelling us what you've already said doesn't help you or us fix the problem.
A notice to EVERYONE who has posted here with a computer problem, I highly encourage you to keep current with the forums, even if it's browsing for 10-15 minutes during lunch, or before you go to bed at night. There are many things that you can learn and apply to future issues. My goal is to help people get to a point where they can use their own knowledge to help themselves, and others.
Also please use the search button. You've got a 50/50 chance that someone's asked your question and we've answered it.