internal wireless card vs USB wireless G adapter question - Windows XP?

I have two [virus free] computers sitting next to each other:

Comp. A - a laptop with an internal wireless card (Intel PRO/wireless 3945ABG)

Comp. B - a desktop with a USB Wireless Adapter (Linksys WUSB54G v.4)

Both computers have the latest drivers, both are connecting to a D-Link Airplus Xtreme G Wireless router, and both can access the internet. Despite sitting next to each other, Computer A connects at 54 mbps with a signal strength ranging from good to very good, while computer B connects between 6 - 24 mbps and occassionally "limited to no connectivity" Additionally, online download / upload tests confirm that d/l speeds of Comp B are about 50% and upload are about 20% of A

Is there something I can do with the Linksys wireless adapter so it performs as well as the Intel one? Any firmware, 3rd party drivers, etc that can boost connectivity? OR, assuming it could be poor technology from Linksys, does anybody have recommendations to other better performing wireless adapters?

First understand that the USB connected adapter will be a bit slow due to USB baus. Other than though there are things you can do make it better

1) experiment with placement of the adapter try getting it to a place that improves reception. Often slight changes in placement result in dramatic improvements to your signal quality.

2) see if there are any updates to your routers firmware.

3) configure your wireless router to support G only not mixed mode,

4) tweak advanced settings on your adapter so all options are on max power. A desktop does not need to use power management on it's wireless adapter.

Good luck.