WMP - Stop working message - What's wrong?

I have some new input about my problem:
I've notice that if i open the folder C:\Programfiles\windown media player and execute the WMP.exe file and choose to open some video it works fine!
The problem is that when i choose to open a file with windows media player it will automatically open with the WMP exe file from C:\Program files (86x)\Windows Media Player.
Something similar is hapenning with internet explorer. I get the same message as with the windows Media Player if i open using the icon from Program files (86x). But it works fine with the icon from the program files!
Why is this happenning if i have a 64 bit operating system??????
Please help!
My problem is not solved because i need itunes and quick time to work, and my system don't accept the 32 bit instalation for this programs because it automatically detects that i'm running a 64 bit system, but when i install the lateste 64 bit version it is instaled in the ProgramFiles (86x) folder and i can't run the programs properly!
What a mess this 64 bit operating system!!!

By the way...if that helps: Windows Media Center and Windows Player Classic (64bit version) are working fine in my system....