Go looking for which Dell it is, ok found LGF sale thread,
so we have
DELL Latitude D505 - XP Pro, CD ROM, 512RAM, 1.6 GHz Centrino, 40GB HDD
Built in wifi (found about 10 wireless networks, 3 unsecured!)
no known faults - software has not been reloaded so there might be some chuff left over from previous owner.
I'd reinstall myself, is there and XP Product Key sticker on the bottom of the laptop ?
Anyways
If standard it should be a b/g modem (Intel Wireless 2000)
Is it connecting though the Intel software or WindowsXP standard. If possible disable the Intel software for now.
You sure you are typing in the correct password ?