PC boots properly, but flashes on and off instead of showing login

Ok, so, I recently had my Dell serviced to replace a bad LCD panel. Also got a new chassis, mobo, CPU fan, and heat sink. All was going well, but I discovered I could no longer put it in hibernate mode. I went to https://support.microsoft.com/en-us/kb/920730 and used the Microsoft Fix It 50462, ran it, which didn't resolve the problem. I think I went in the advanced power settings and changed some things about what to do when the lid shuts, push the power button, etc. I then used it, and, when I was finished, put it in hibernate mode. All was well until I tried to turn it back on.

Now, it looks like it boots properly, but when it gets to the point where it shows the Windows wallpaper and would normally ask me to log on, the screen sits for a moment, and then starts flashing on and off. It won't stop, and it never gives me the opportunity to log on.

First, I tried running the diagnostic tool at startup, and there are no hardware errors.

I've tried using the recovery tool, but it always fails (it looks like it succeeds, but it says it failed upon reboot). I've also tried going into cmd, and using

Code:

powercfg.exe /hibernate off

but it throws an error saying

Hibernation failed with the following error: The request is not supported.

The following items are preventing hibernation on this system.
There are one or more legacy drivers installed:
VgaSave
An internal system component has disabled hibernation.

It gives the same thing if I try to turn hibernate on.

I've tried creating a bootable USB recovery stick, both using the Windows USB/DVD download tool, and also using Rufus, both from a Windows 7 Home Premium ISO I downloaded from MS Dreamspark. This caused an issue with the BCD, which I have resolved, but I'm still back in the same place.

I can boot in safe mode, and I have tried uninstalling the drivers for my Nvidia display adapter, rebooted, and the issue was still not resolved.

There is nothing in my BIOS about any sleep or hibernate functions, thus, nothing for me to change.

I tried

Code:

bcdedit /deletevalue {3d8d3081-33ac-11dc-9a41-806e6f6e6963} inherit

as suggested at http://answers.microsoft.com/en-us/w...c-043daff7d857, but I got

An error occurred while attempting to reference the specified entry.
The system cannot find the file specified.

I did see something about disabling FastAccess at Windows log on screen won't load just keeps flashing, which I haven't tried, but a) I like FastAccess, and b), it was working fine with FastAccess before the hibernation situation, but I'm willing to try that if necessary. And, if I do do that, how would I go about re-enabling FastAccess afterwards and prevent this same problem from reoccurring?

Any ideas?