first is pretty easy, find a file that's less than 100px by 100px, that is also less than ummm 20kb.

i've responded to a post like this before, so do a search about avatars and you should find it and be able to find out how to do it... it's been written in the past day or two so it shouldn't be that hard to find, but i'm too lazy (and waaaaay too tired) to find it now (since it's 2:30am for me). if you don't find it right away, i'll look for it when i get to work tomorrow.

as far as the print screen button not working, you have to own some sort of photo-manipulation program in order to be able to paste a screenshot... hell, even microsoft paint will do it... so when worse comes to worst, just paste it in paint and then (if you can) resize it to match something close to 640X480... cause that's what the moderators like