sorry if this sounds like a noob question, but ive made some models that i'd like to show off, but i dont know how to get a picture of them (i'd just take a picture of them ingame, but i'm having trouble getting them to work ). Is there a function in XSi that lets you take screenshots?

no there is not (as far as i know) but you can make a screenie with windows: press the Printscreeen butto 2 seconds, then open paint and press STRG+V now save the image and you are done

While ingame if you press the "prt scr" button on your keyboard you will take a screenshot and the image will be stored in:
C:\Program Files\LucasArts\Star Wars Battlefront II\GameData\ScreenShots

If you're trying to get a screenshot from XSI just press "prt scr" then just open MS Paint(included in Windows) or any image editing software and press ctrl+v to paste the image from the clipboard and save it somewhere.

alright thanks guys. got my screenshot in the model showcase thread. thanks for the help

Just a note, that method works with GIMP and mostly any other image editing program, (Not just paint).