Isn't it crappy when people ONLY come to you when they need something?
I'm like you. I don't mind helping friends (even if I'm not as technologically advanced as you are), but I also expect THEM to be putting something into the relationship as well!
What's funny is that they don't even realize they are USING you! If you say something to them, they try to make you feel like you are in the wrong.
So yeah, I get it.
What's funny is there's a lot of really nice people out there. You help them do their thing, they ask you over for dinner, make you a batch of cookies, etc. to "pay you back."
Hard though it may be, it sounds like an honest conversation is in order ... along the lines of mentioning that you are feeling used ... and can't really help them anymore.