Task Manager Un-openable

I'm having a problem with being unable to open Windows 7 Task Manager with any method. Here is the time sequence.

1) Recently had downloaded Process Explorer to see how it worked. Decided I didn't like it and removed it (oddly, wasn't on my Remove Programs list and had no uninstall file).

2) Needed to use task manager, did Ctrl-Alt-Esc and nothing. No messages, no task manager, no apparent attempt to run task manager.

3) Tried the same thing with Ctrl-Alt-Del and selecting Run Task Manager. Again, nothing. No messages.

4) Scanned my system with multiple malware and anti-virus programs (reputable ones). No changes.

5) Checked the registry for remnants of Process Explorer and removed. No change. Ensured Task Manager wasn't disabled in the registry.

6) Tried to run Task Manager from the taskbar. Got an error on taskmgr.exe "The parameter is incorrect."

I can only assume this is the problem, however I cannot find any fixes for it. Any suggestions?

Sadly, it only had a couple days back in System Restore, which was after the issue started.

And when I attempted a repair install, it did not find anything wrong as far as I know, but when I rebooted I couldn't access the internet, nor get windows firewall correct, and a couple other problems. That's when I did the restore.

Is there any way to tell what the parameters for the file should be and change mine to it?

Did you select to replace Task Manager with Process Explorer?

If so, get another copy of Process Explorer and see if you can undo it from within that.

Replace Task Manager: Select the Replace Task Manager entry under the Options menu to have Process Explorer execute instead of Task Manager when you launch Task Manager. Note that this is a global setting that affects all users regardless of how they start Task Manager. After replacing Task Manager the menu item renames to Restore Task Manager and selecting it removes Process Explorer's association.

This might work

Re-Enable Task Manager and Open It

SIW2 said:

Did you select to replace Task Manager with Process Explorer?

If so, get another copy of Process Explorer and see if you can undo it from within that.

Oddly enough, though I never saw anything that said Restore Task Manager, reloading the program and doing what you mentioned worked.

Thanks for the assistance everyone.