No access to the Windows Installer Service!! (please help me asap...)

Hey

THIS is one of those excrutiatingly annoying problems that I've been trying to solve for the past 2 weeks through Google, Windows Help and God knows what else ... but nothing. I seriously hope anyone out there can help me ... it'd be much, much appreciated.

I have a problem with Windows Installer Service. As such I cannot install certain videogames (such as FIFA 08 or FIFA 10), certain programs (such as Microsoft Visual C++ 2010) or other bunch of stuff.
Strangely however, my "Windows ® Installer. V 5.0.7601.17514" is up-and-running through CMD and I also find it in Regedit. :sarc:

Why doesn't it work, please? Do I have to delete Windows Installer completely and then reinstall it again? And how do I safely delete Windows Installer and where/how do i reinstall Windows Installer, please? :huh:

Please help me. I'm quite desperate here!

Many thanks in advance,

Bye for now

P.S.: I have also added no less than 3 Print-Screens. Although they're mostly in Dutch, the error is always the same; stating that Windows Installer cannot be found ...

Please! Somebody, help me! I'm drifting on an ocean of questions and problems regarding this Windows Installer Service and I need urgent help!

thank you