Computer problems , Hard drive related?

I built a computer and it’s been up and running for almost 3 years. Nothing in this computer is older than 2.5 years. I recently went to upgrade from windows vista premium to windows 7 ultimate. Before this the computer had no problems. During the upgrade the computer hung. Now when I restart or start the computer the computer boots up past bios fine then will go into a stand by mode or sleep but nothing will wake it and I have to hold power button in to shut it down or restart it. The computer comes on and then loads bios and the monitor will briefly display no input from computer and then the computer shuts down but doesn’t power off. The power light will stay on and the hdd light will light up if I open the CD rom other than that nothing at all.

Not sure what the correct answer would be without lots of debugging. What does the computer do when the HDD is unplugged.

If it gets further along to the startup till it asks for an operating system then I would zero the drive and see if the Win7 install completes.

The port the HDD plugged into my be faulty, try another port. The cable might be faulty, try another cable. There is a long list of things to try. These few are some of the usual or simplest to test for.