Need help with configuring wireless networking, I think

Can someone help me with setting up my laptops for communication on my home network?

I have 5 pc's connected to my home network, 3 laptops and 2 desktops ... all were running  windows xp (pro or home) ....they are all connected via a linksys wrt160n router ...while my online (internet) speed was 5mbps, any and all file transfers between the machines was around 50mpbs - 100mbps .... which was fine, very satisfactory for my usage.

So now the problem, I recently purchased 3 new dell laptops (a studio 1749,  a studio 1555, and some other cheap one) ....  all three of these laptops use Windows 7,  the 1749 using Win7 Pro, the other two using what ever cheap version of win 7 that came with them) ... here's the problem, while each of these laptops connects to the internet at 5mbps, their machine to machine file transfers are only about 2 - 3 mbps. This is a MAJOR difference compared to what it used to be, and only came to light when I backed up the one laptops files (60gb file size) .... then put on the new laptop, tried to transfer that massive file onto the new one, and it took 3 days, non stop, for the transfer to complete. (it was during that transfer I noticed the transfers were only going at about 1.5 - 2 mbps) (even commnunicating with the one desktop which is still using windows xp pro)

So is there anything I need to do to properly set up these new machines for networking or something? If there is I sure don't know what it is, I had used the old machine just with their  defaults . Nothing special I had to do.