I'm going to assume you've already rid yourself of 2.4GHz cordless phones and 2.4GHz wireless video systems, as well as any Bluetooth wireless keyboards and mice using the 2.4GHz band. That's the first step to eliminate interference with your 802.11g network. Of course, if you live in an apartment or condo, you're still subject to the interference caused by your neighbors.
Does the WRT330N state the wireless sync speed? If you are sync'n at significantly less than 54Mbps, then that would suggest either a weak signal (which you do not have) or a lot of interference in the 2.4Ghz band. With most drivers, Windows XP will report 54Mbps anytime that you connect with 802.11g. However, that has
nothing to do with the actual sync rate.
The below screenshots are a perfect example.
Wireless sync with 2.4Ghz wireless video system on
The x.x.x.112 system is the Playstation3 in my living room. The x.x.x.102 is a PC in an office downstairs. That particular office has a lot of RF interference when certain equipment is on. I turned that equipment on for the above screenshot, and XP showed 54Mbps with signal strength of 4 bars. But look at the actual sync speed, as reported by the D-Link router. The wireless errors reported on the D-Link's status page increment regularly.
The below screenshot is with that equipment turned off. The signal strength is similar, and Windows reports the same 54Mbps, but the actual sync speed is very different. Wireless errors, as reported on the D-Link's status screen, are largely eliminated.
Wireless sync speed with 2.4Ghz wireless video system off
I live in a suburban neighborhood, so there is a fair amount of distance between my home and the next. Hence, interference from other peoples' 2.4GHz devices, such as cordless phones, cordless mice/keyboards, wireless video cameras, and the like is kept to a minimum. If you live in an apartment complex, there is almost certainly more interference in the 2.4GHz spectrum, even if you see only one or two 802.11g networks. Also remember that Windows will only show wireless networks that broadcast their SSID; many enthusiasts disable their SSID broadcast for security reasons.