Can connect to Belkin router then drops out

I'm running three HP laptops - 2 use Vista, the 3rd uses XP. Running a Belkin
N1 Vision router. Only the two Vista machines can successfully connect and
maintain a connection to the network. The XP laptop connects and stays
connected for up to several hours maximum, but then drops out and continually
tries to 'Acquire IP address'. I have other wireless devices connected to my
network and generally have no issues (e.g. Airport Express; PS3, etc). I only
have issues with this one laptop running XP. Apart from upgrading to Vista on
this troublesome laptop (which I can't do as it's an employer provided one),
would be grateful for any suggestions.