Hi

From what I've found, this usually occurs if you have an invalid directory path somewhere.
Here is a small program that will check your directory paths, If it comes up with an error or if any of the boxes come up empty, you have a problem. This program simply checks your system and personal directories one by one and asks you to confirm that they show up. Try this out and report back please.

Hi

No prob bud, I usually try to help those that nobody else seems to be able to help.

As long as that little program didn't come up with an empty box, or say that there was an error in the path, everything was found to be in order then. And your list shows that all your user and directory paths are intact, so that's it for that idea.

I am NOT a fan of Registry Cleaners, I think they're simply a problem waiting to happen in most cases. I have tested many of them a couple years back, and every single one of them had important keys in the Clean list once in awhile, and it takes an experienced eye to be able to catch these before they're deleted. Problem is, probably 90% of the people that use them don't have that level of experience to be able to recognize a key that shouldn't be there, so eventually something really important is bound to get deleted.
Did you actually use the cleaner to "Clean" up some (supposedly) useless keys?

Orphaned registry keys do not slow the system down. Loading the entire registry takes 2 or 3 seconds, so just what extra time does a few orphaned keys cost you?
Orphaned keys aren't accessed by anything....they're orphaned...so there's no lost time for anything there either. And 500 keys might take up a whole 1/2 a megabyte (if that), so what's a few orphaned keys going to cost space wise, when HDD's are now measured in 100's of Gigs, or Terabytes now.
I've never needed one in all my years of using Windows OS's, I've worked Tech help boards for 13 years now and I've never recommended one either, and the many Ultra-Expert tech friends I have made in those 13 years all agree about Registry Cleaners...not needed and possibly dangerous!
I have Literally seen 100's of systems corrupted by Regisrty Cleaners, far more than by any other user program I can recall. Windows Registry is just not a place to go mucking around with, so why take the chance.
The ONLY time I would say something different is when a device manufacturer says that all previous bits of it's software must be removed before a new driver/patch can be applied, and they offer a "Cleaner" program to automate that process or they guide the user to what keys need deleting.

Ok, back to this issue...is it only drivers that won't install? Or certain drivers, like the Nvidia display drivers, or is it ALL drivers now? Have you tried uninstalling a device's drivers that's not boot critical and then try to reinstall it's drivers to see if they'll load?
Are you sure you changed the DEP settings back to the default setting, only on for Windows services or programs?

There is also a "Block" put on software that's d'oaded sometimes and I haven't figured out just what the criteria for this is, but right click the driver and select Properties. On the General tab, on the bottom there may be an "Unblock" button if it's been blocked, try that out. Also you can try right clicking and select the "Run as Administrator" option, that sometimes makes a difference.