Being a Mac user, where QuickTime is heavily integrated into the OS, is used in almost every application and works very elegantly, it's easy to forget what a horror it is on Windows.

For me, QT would occasionally blow up when installing a Windows service pack or security update, although I'm sure it's just coincidence that it happened three or four times.

I had one problem where whenever anything to do with QT appeared on the screen, the icons and graphic down the left of the start menu would get corrupted and turn into grey static. This survived even through a reinstall of QT.