Help needed....Wireless connection to Belkin Modem/ Wireless Router

[#1]

Hi. I recently acquired a Laptop. Previously on a PC on Plusnet just using the Voyager105 modem. All ok there.
I had lying around a Belkin F5D7632-4 ADSL Modem with wireless G Router so i plugged the dsl line in, switched on, and seemed ok.
Turned my Laptop on and it found 4 neighbours wireless internet (low signal) and also my Belkin (full signal)
However, when i try to connect it communicates for a bit then disconnects. If h hover over the wireless icon in the tray at bottom it says connected - but the main window on screen says disconnected? Then when i try to open internet the page not found rubbish comes up.
Are there any special settings for this??? I am asking because I piggybacked a neighbours network (low signal) and got on ok?
Any help would be appreciated
G

[#2]

It sound like a sleep setting either the router or the laptop turns off the wireless after so long of no use to save power(most likely the laptop).
Does it only do it after its been idle? Is it worse on the battery? Try looking at the wireless setting and look for sleep/powersave options