Slow airport transfer over network please help!

K this is kinda a mac/pc question but I don't know where else to ask. Here is what I have, PowerBook 12" with AirPort extreme, Belkin 54g wireless router, and Dell Dimension 8100 with Trendnet 54g wireless card and XP Pro SP2. Here is my problem. XP shows I'm connected at 54g. The router is also 54g. When I try to transfer a file over the network it's SO slow, like 802.11b speed. I used to have a b router and would transfer a 700mb file over the network in about 20 mins from Dell to PowerBook. I then got a Belkin 54g router, connected the dell with 100mbps ethernet and powerbook airport extreme. Transfering the same 700mb file took me 4 minutes over this setup. However, with a 54g wireless card in the dell, its gone back to taking 20 minutes or so. If I create a peer to peer network and connected the PB directly to the Dell it transfers very quickly, definately at 54g speed. I don't understand because the router is set for 54g only, and the dell says I'm connected at 54g. I don't know how to find out if PB is connected at that speed but I'm assuming. Why would this be so slow, something wrong with the router? It has updated firmware and such. I'm transfering by pressing command K at the desktop, typing smb://my dell IP and selecting the workgroup share. Is it maybe because of this method im using? Thanks for your help.

How close are the machines to the router? The closer the better. To be honest if your transfering files like 700mb, you might aswell get a short crossover cable.

The dell desktop is in another room maybe 10-15 feet away through one normal wall but its signal is very very high. The Powerbook is in the same room maybe 5 feet away. I dunno its weird because when the dell was connected via ethernet it was soooo fast..