Black Screen after login, explorer.exe faulty, usual fixes dont work

Hi! I'm not sure this is the right section, but since a Virus started it all, I figured it is.

Short story:
-got Virus, got rid of it (probably)
-used ccleaner to "clean" registry, which screwed it up (probably)
-now get blackscreen after login, explorer.exe doesn't start and crashes 5 seconds after starting it from task manager
-same in safe mode
-everything else seems to work
-tried most fixes suggested by googling the problem (win startup repair detects no problem, shell of winlogon reg key is "explorer.exe", sfc /scannow tells me nothing is wrong.

Complete story:
I have Win 7 home premimum 64 bit with all updates. It was preinstalled on a custom built latop from a merchant in Germany

The other day, I got a trojan virus from foolishly running an executable. Its attempt to connect to the internet was blocked by my firewall (Comodo) and Microsoft Security Essentials identified and deleted the virus.. I checked online whether any additional removal steps are necessary for that trojan and according to microsoft, that is not the case.

Still, I decided to do what I did years ago with Xp in such situations: Download a battery of scanning/removal tools to be sure.

I started with ccleaner and unfortunately did a registry cleaning, doing a back up for the first run. But then I rescanned and kept fixing reg issues till none where left. I did not create backups for those additional runs of ccleaner.

When I rebooted my computer, I ran into my current problem: After login, I only get a black screen. No explorer. I can conjure up task manager and run processes from there, but not explorer.exe. When I run explorer.exe, it appears in the processes but then vanishes after 10s seconds. If I try to see its properties in task manager in that 5-10s window, taskmanager crashes.

Things I've tried (using an usb which I accessed with firefox, now I have a portable file manager though):

-safemode. Same problem
-restoring registry with the one backup I made before running ccleaner. no result
-checked whether the entry in the shell of r winlogon is only "explorer.exe". it is
-windows start up repair. Says nothing wrong
-sfc /scannow. Says nothing wrong
-scanning for viruses using MSE. nothing found
-scanning for malware using superantispyware. nothing found
gonna try malwarebytes, spypot search and d and tdsskiller (a rootkit remover from kaspersky) later, but it seems like that's not the problem

one last option i found was

I was able to narrow down the reason. Windows Management Instrumentation service is the culprit which is stopping the windows desktop/taskbar from loading. I went to msconfig and disabled it resolving my issue.

for a problem very similar to mine (explorer exe vanishes after 5 seconds)

But other than that I'm out of ideas. Does anyone have an idea as to what I could do? Since win 7 came pre installed with drivery and everything by the merchant, I would hate to have to reinstall windows 7. The chance I get everything working seems remote.

I've already done everything mentioned there without success...
except system restore points, i dont have any

the firewall blocked outgoing network traffic from the trojan which microsoft sec ess then deleted

I don't think so. Control panel seems to rely on explorer.exe. when i type 'control' in cmd nothing happens but
in the task manager i see that explorer.exe, control. exe and WerFault.exe appear and vanish after 10secs

is there another way to create a new user?

ok managed to create one by spamming control in cmd safe mode. then i had like a 7 sec window to create a new user before explorer exe crashed. took me a few tries but now i have another admin acc

but it has the same problems

My advice is that you need to re-install your Windows 7 again. The registry cleaner deleted the started config together as the backdoor trojan tricked all of us (software inclu.) to delete all the functioning registries.

sometimes our system reserves also get infected thanks to dll that got loaded during startup.
The whole HDD got to be formatted.It's a very troublesome task.