Really slow PC to PC network speed

Current setup is my home PC (dual 1GB Marvell LAN ports, only using one), wife's laptop (Dell Inspiron with WiFi .b 54Mb), we are both running Win7 Home Premium (me 64, her 32) RCA Cogeco cable modem, Belkin wireless N router model F6D4230-4 v1000)... cable comes into modem, modem goes to router, router goes to my PC laptop picks up wireless signal (well, so do our phones but whatever, it doesn't matter if they are in WiFi range or not for my problem)... point here is I can download a file at 1.3-1.5MB/s (wired), she can download at about 1.1-1.3MB/s (wireless)... we can transfer files between our two computer at a whooping 800k-1.2MB/s. Yes, you read that right. It's faster for me to download than it is to go computer to computer. I've tried all the tricks... Ipv6 gone, RDC gone etc etc...homegroup well, gone... I've changed cables around (new, old, different ports) nothing. This topic has probably been beaten to death but doing any kind of backup, sharing, streaming etc is just painful.

Is it the same result if you plug her laptop directly in to the router? Also turn off the wifi on the laptop just in case it use wireless instead of the direct connect

hold on, you said you laptop Wifi is wireless b at 54?
Wireless B is like at 11mbps, where G is at 54mpbs. Can you clarify what one it is?

I am guessing you using wireless G because B is very old,
I have always found the real speed of wireless to go about haft of the rated speed, so your at 54, haft of that 27mbps or 3.3 MBps. So you should be getting at least 3.3MBps between the computers over WiFi.

I since you got good speeds between the two computers directly connected, I would start looking at the WiFi as the problem.
I would first check to make sure, there is no other neighboring wifi hotspots that are on the same channel as you. That can cause interference.
Next I would check to make sure you are actually getting a 54mbps connection, there are a few ways to do that, I always look at the taskmaster under the network tab.
If that all looks ok then I would tell your router to only accept wireless G connections, some times routers have a hard time jumping from wireless N down to G. then back again.
And last I would check for new drivers for your wireless card.