Toshiba wireless issue

I know there are tons of forums on this subject but I've trie tons of things and am running out of ideas and things to try that i find. My wife's laptop disconnects from the internet seemingly at random, she's using 32 bit xp. My laptop has been connected nonstop for months with vista 32bit. I've tried changing settings in her computer so it always uses max power (thinking that it would should down for power saving). I've raised the wireless router above all furniture. I've updated the network card to the latest driver. I tried using intel proset wireless which seemed to decrease connection time. Changed the channel on the router several times. There are a lot of wireless connections around us as we're in military stairwell housing. I chronologued memory usage thinking, it just couldnt keep up for some reason... which I did learn it needed a couple hundred more mb's(and i traded my comps 1gb for a 512) problem still persisted, also teste her memory prior to that, but that's because it likes to hang on webpages sometimes. is there anything else i can do to help he comp stay connected? Thanks, for any help.

kurt