So, what programs make you sigh when you sit down at someone else's computer?
Pretty much any bundle-in browser toolbar (Yahoo!, Google, etc).
Pretty much anything Yahoo! for that matter.
I used to really hate RealPlayer and QuickTime but it's been a really long time since I've used them or seen them so maybe they've changed.
Any sort of software that comes with a digital camera, like Kodak EasyShare software for photo albums and things.
And last but not least: OSX
EDIT: This one is kind of the opposite of your question. Things that annoy me when they're not
on someone else's computer: