tl;dr Windows used to be on C:, but after a system restore it's changed to D: I know how to fix it with regedit.exe , but nothing will run in safe mode.
Slightly longer explanation I was stupid and deleted some unneeded partitions on my harddrive (something I've done before without incident). Afterwards, the computer couldn't find the boot disk (!) so I used the instructions found here to make the required drive the active drive.
After a quick startup repair, Windows loaded again. Only now it says "This copy of Windows is not genuine" in the corner (even though it is genuine), and nothing loads: no start menu, task bar, desktop. The task manager loads, but there are only 3 processes running, and explorer.exe and System aren't one of them!
When I boot into safe mode (with or without command prompt... both do the same thing) there's still no start menu, but the task manager at least shows an appropriate-looking number of processes. I go to New Task, type regedit.exe, and nothing happens. If I browse to regedit (btw, this is how I can confirm the drive letter changed to D) and then try again nothing happens. The window blinks but nothing opens.
I tried running a repair install, but those instructions assume that Windows is properly working.
Is there some other way to safely change the boot disk letter or otherwise troubleshoot why nothing is running?
Computer Computer Details: Win 7, Dell but with a new HDD/OS install (old harddrive died... which is what started all this in the first place)
THANK YOU SO MUCH!!!