AFAIK those screws hold the plastic cover(s) on.
If you're wondering how to improve the airport reception, then get a wireless PMCIA card. You can sell the internal card or keep it, your choice. I've got a Aironet 350 (802.11b) and the diff in the PB-400 was night and day. Where I previously had zero reception on the patio with the internal airport card, I suddenly had full reception with no loss of bandwidth.
Nowadays, I might go with a g-card, but basically it'd be a question of price.