|I would not recommend that.|
Reassemble as a bench test, just MB, CPU, heat sink, power supply, one stick RAM, monitor using onboard video (if available), keyboard (preferably PS2). Begin by resetting CMOS before powering up. If you get a post screen and warning that you have no hard drive, reset defaults or optimal settings. If not post then switch RAM and slot you are using for the memory. If no post then the motherboard is suspect. If still gets to this point (posts), add components one at a time and test (hard drive last). Run Memtest86 through all tests, NO errors are acceptable! If everything else tests OK then install the hard drive. If you do not boot with the hard drive then try a start up repair on your Vista. If that does not work then try reinstalling Vista (full format). If it cannot install then the hard drive is suspect. Use hard drive mfg's utility to test hard drive.
You have to be a little bit crazy to keep you from going insane.