Wireless adapter loses signal :(

im working on a friends computer. When i turn it on its network adapter (Dell Wireless 1450) connects to his linksys router, but after awhile it automatically disconnects. Ive tried lots of things (uninstalled the adapter, reinstalled it, changed the wireless channels etc.) Im running out of ideas, im scared if i reinstall the OS, its just going to happen again. The funny thing is that his laptop and mine can connect perfectly, but the desktop cant. Any help would truly be appreciated. Thanx