wireless range?

hi, im new at this forum and i dont know much about wireless things. Im thinking about buying a wireless usb adapter for my laptop that doesnt have one built it, since its old, and i want to get acess to the internet, so i used one of my old ones, but i had to more close to the router than were i wanted to use it. so my question is:

how can u tell what the range of the connection is for a wireless usb adapter?

the one i have is here, Amazon.com: NetGear WG111US 54 Mbps Wireless USB 2.0 Adapter: Electronics

About 50 m.It really depends on a lot of things like link speed, wireless standard(a,b,g) router position...

oh ok thanks.