Alright, Ive had this problem for about 4 months now and its been driving me crazy. Ive tried literally every possible solution on the first 100 results from many different search queries and nothing resolves it for me. I'm using Windows 7 x64 with and AMD processor. Here's what happened this time and finally put for over the edge: I have a problem where I need to now re-install itunes for it to work, but becasue the windows installer is broken, i cant even uninstall any programs, let alone install something new. I've done a few temporary fixes (setting the image path to 'C:\\windows\syswow64\msiexec.exe \V', unregistering the service and re-registering from safe mode) that worked once or twice, but nothing resolves the problem entirely, and none of the 'fixes' can resolve the issue im now having with itunes. First of all, when I try to unregister the msiexec.exe in the system32 folder, I get the following error: "The program or feature "\??\c:\windows\system32\msiexec.exe" cannot start or run due to incompatability with 64-bit versions of Windows. Please contact the software vendor to ask if a 64-bit Windows compatible version is available." Once I decided I couldnt get the 32 bit version to work, I edited the ImagePath key in the registry (Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msiserver) to point to the 64 bit version of msiexec. Unregister, re-register in safe mode and then try uninstalling itunes again. This time I get the error: "The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installer. Contact your support personnel for assistance" Since im sure its not the former (safe mode) it must be that windows installer isnt correctly installed. How can I fix this?

I suggest you run In-place Upgrade to repair the system. Your personal data and programs will not be removed. However I still suggest you back up important data before In-place Upgrade.Arthur Xie - MSFT