-Spock
Some stuff that are a little more exotic:
-Propensity to spontaneously change its settings.
-Lack of common sense in some settings
For example, When I'm working, I wire my 12PB to ethernet, and create a private wireless network so my T30 (XP Pro) can bridge in - two machines, one connection, no hubs or basestations. Every now and then, the wireless network setting and LAN network setting in the XP box will start DHCP'ing to each other (incestuous isn't it?) thereby removing itself from net-workability. Why didn't MS think that this was even a possibility of occurrence when they wrote this? Stands to reason that if one active connection happens to grab the same IP another active connection is serving in the same OS instance, may-not-be-a-good-idea.
-XP is in my face. I'm skilled a teensy bit above the average user - get that wizard out of there. No more clippy! If xp want to tell me something, fine, let it, just don't unfocus me from my current task so I'm not typing into oblivion. (I've noticed even the Mac versions of MS products usurp focus too).
-Errors are terse, and accusatory - just pisses me off.
-Help files are rarely useful - Don't tell me that I can to the wonderful thing I am asking about, tell me how to use it!
-I'm not the master of the system, MS is.
Ever try to remove MSN Messenger (just one example)? The icon and GUI goes, but the functionality stays - so when I connect, it kicks off an already connected machine.
-Needs a lot of hand-holding. I'm running Oracle, VPN, Apache, TomCat, CVS, and a lot of other things. I need to do my work, not constantly tweaking the damn thing so that I can do that work - again, get out of my bloody way!