There are a lot of reasons why you'd get different speeds. One obvious
reason might be that one computer is faster or better equipped.... faster
hard drive, more memory, faster processor. But that still shouldn't account
for that much of a dramatic difference in throughput.
Here's what I'd recommend.
From the slow machine, go to http://www.yqcomputer.com/
. On their BROADBAND
menu, go to their Broadband Tools, and check out their SG TCP/IP Analyzer.
There they will check out your network settings and make recommendations.
They also have a phenominal tool that you can download, called the SG TCP/IP
optimizer (it's free), which you can use to tune up your settings with a
couple clicks of the mouse instead of digging through the registry. Or, if
you prefer, they do have all the gorey details explained at speedguide.net.