Windows cannot find "...". make sure you typed... error

Hi,

I'm receiving this error when executing some executables: "Windows cannot find "[name and path of the executable (.exe)]". Make sure you typed the name correctly, and then try again".
I may understand receiving such error if I were executing a "bad" shortcut, but in this case, I'm directly launching it from windows explorer. Since I'm not receiving that error for all my programs, I suppose there might be an issues in the registry or somewhere else.
I then reinstalled the software, and got the same error.
I tried launching it inside a freshly created account and I got the same error.

Here are more details about my setup:

* Windows 7 pro 64 with all updates
* AMD 3800+ with 4GB mem
* Executables: "steam.exe" ; "googletalk.exe"
* Hard drive SMART status OK
* ZoneAlarme security

I'm also using smart defrag, tuneup utilities and Ccleaner to optimize my system. I hasn't made any changes manually in the registry.

Any help would be greatly appreciated

I would not run TuneUp utilties or otherwise tweak Win7 beyond normal system settings. It will not tolerate it and causes many problems. No one here recommends Zone Alarm that I've ever seen either.

It makes me think you might benefit from the Best Practices given here to obtain and maintain a perfect Clean Reinstall - Factory OEM Windows 7 which are the same for retail.

In this case you may have a Default setting which has slipped. Check in Control Panel under Default settings.

If it persists and no one else has better help then I'd run SFC -SCANNOW Command
or a Repair Install