my computer can not find the install folder or the source for itunes 10.4 so it cant be removed and I cant intstall the new Itunes

I have the same problem with 10.6 update, I tried deleteing the folder from program files, still no use. VERY stuck on this!

my computer can not find the install folder or the source for itunes 10.4 so it cant be removed and I cant intstall the new Itunes what do I do ?

Doublechecking before proceeding. Which particular .msi file is the message saying can't be found? (Several different .msi files can be mentioned in this particular context: itunes.msi, bonjour.msi, AppleSoftwareUpdate.msi, etc.)