Wireless Trouble

I have a wired network, with a DLINK DGL-4300 wireless 108G gaming
router.

I recently bought a wireless usb adapter, a DLINK DWL-G132 "highspeed
2.4ghz 802.11g wireless 108mbps usb adapter."

I've got it working, and it can connect to the dlink router. However,
transering files is painfully slow. In fact, the transfer rate is
about the same as my internet connections main downstream rate, about
2 to 3 mbps. When transfering huge files, it's so slow.

What speed should I expect? Any ideas where to look in the configs
for fixes?

Thanks!