I'm not an IT person (you know, the desktop support guy, system admin or the computer dude,) but I have hired them, had them fix my mistakes and had them look dumbfounded at me on several occasions. From my experience, and what I've gleaned from our terse interactions, I've put together this list of things you should not say to them.
1.You're a chick?
Just from the title of this list alone, I'm in deep shit. Not all IT people are guys. When an IT chick shows up, don't mention it because she's heard it hundreds of times already. Just let her fix your mistakes and please don't ask her if she is into Manga.
2. I think I fixed it.
IT people don't care that you fucked something up. It's bound to happen. What they don't like is when you attempt to fix it after you tell them there is a problem. Especially if it is hardware related and they've dragged their ass all the way to your desk. Just pretend like you didn't fix it and ask them if they are with the Alliance or for the Horde.
3. Are you with the Alliance or for the Horde?
It's not the assumption that a computer person might play a MMORPG. They probably do. The issue here is that you are pretending that you care enough to know and to take that first step into their imaginary world. Unless you are willing to discuss the newest patch or the most recent guild politics, you should just keep your yap shut. Besides, they probably play Guild Wars.
4. So, is this all you do all day?
Bad question. This oozes with the assumption that they don't do anything all day. And sadly, the real question should be, "What don't you do all day," and the answer to that is "I don't get important stuff done because I'm spending my time re-installing Windows on your computer for the third time."
5. Can I bring my lap top in from home?
6. Would you like to go on a date?
Office relationships never work out. It screws up your and your co-worker's production. When you inter-office date an IT person, it throws off the whole business. IT people need to be surly to get their jobs done. If they are happy, I'm not sure what would happen to the network. The only case of when dating the IT person will work is if you dump them and completely break their heart. Then the company is secure for months as they brood and work for 18 hours a day. If you only half break their heart, you are in "Say Anything" territory and nothing is creepier than an IT guy standing in your driveway with a laptop over his head playing an MP3 of "In Your Eyes."
7. Don't you think case mods are gay?
They are gay, but IT people need a creative outlet. Just say that you saw an interesting case that was a 1:73 scale model of the Farscape, Peacekeeper Pantak Class Vigilante.
When they stare at you for a moment and don't say anything, hold up this list and they will understand.
8. Bet you've seen some great photos and videos while digging through people's computers.
Yes they have, but not because they were nosing around like you are suggesting. Having a 120GB movie slowing things up requires investigation. So does any collection of 1,500 photos with the words wife, anal, teen or spycam in the filename. So, yes, they are digging through your photos and videos, but dammit, it's for the good of the company.
9. Did you see the Matrix?
Of course, asshole. Everybody did.
10. Do you have a blog?
Yes, they have a blog. But it's probably a pretty well laid out, informative page instead of this cookie-cutter crap. They probably talk about everything but work, though they might bring up you on occasion and how you almost broke their heart and that their mood is sad and they are listening to the "Say Anything" soundtrack.