Q: iTunes 10.6.3 won't install, any help?

But now I can't install iTunes

Do you get an error message when you try to install iTunes? If so, what does it say? (Precise text, please.)

iTunesSetup/exe is not a valid Win32 application

In the course of your troubleshooting to date have you worked through the following document?

iTunes: Windows reports that "iTunesSetup.exe is not a valid Win32 application"

Perhaps try downloading and saving a copy of the installer to a different PC. (If you're on a 32-bit Windows system, try to download on a different 32-bit Windows system.) Copy the iTunesSetup.exe installer to an external hard-drive, or a large-enough thumb drive or burn it to a CD-R. Carry the installer back to your PC, copy the installer to your hard drive. (Don't run the install from the ExHD, thumb or CD-R.) Start the install by doubleclicking the iTunesSetup.exe file.

You hadn't tried using a different browser previously? (It's about the first thing mentioned in the troubleshooting document, so I assumed you had tried it when you said you had worked through the document.)

Which browser (or browsers) have you tried using so far?

IE and Chrome

I'd try Firefox ... it handles network connections a little differently from Chrome, IE or Safari, so in cases where there's an issue with IE or Chrome, Firefox can sometimes get a working installer (and vice versa, though IE working when Firefox doesn't in this sort of context is a bit rarer overall than Firefox working when IE doesn't).

If still no joy with Firefox, I'd try the download of the installer to a different PC.