Every time i open certain applications in Windows XP (for example Internet Explorer, iTunes) the Windows Installer window pops up, and the application takes a few minutes to load. This happens on every occasio: for example, if i have IE open, and i want to open another IE window, then Windows Installer will start running again. Has anyone else encountered this? I'd appreciate any help or advice you can give. Thank you!

Littleboo

My guess is that the windows installer has detected that something is wrong with an installed program and is trying to do an auto repair. I would imagine that it willl be tricky to work out what's going on.
When the installer appears does it say what its trying to repair?

Have you installed anything new recently, if so try removing that to see if the problem goes away.

if that doesn't work you can turn on Windows installer logging to see what its doing.

There is an article here but its fairly technical.
http://msdn2.microsoft.com/en-us/library/aa369776.aspx