Having trouble setting up my linksys wifi?

i have the linksys router and wifi adapter for my desktop i dont have a wireless net work set up but the adapter is synced with the router when i go online i can get on for about 5 to 10 min then i lose signal but if i unplug my adapter from my desktop and then plug it back ini get back on the inter net but it loses signal every few min and i have to repeat the process why cant i hold the signal? and the router is not to far from the adapter its in the next room not even 15 feet away my computer is an emachines with windows xp so some one please help me out and explaine it as though u were talking to someone completely computer illiterate