I recently was having horrible download rates on some VMWare ubuntu images that are hosted on a beefy Win7 box.
Found a link an article by Dinesh over at Sysprobs.com. Followed steps 1-5 and IMMEDIATELY saw huge improvements in network performance. Thanks Dinesh!
UPDATE #1
I found another tweak that helps (original tweak worked in short term, but eventually went back to slow).
Article by Windows Reference:
Windows 7 Slow network copy.
UPDATE #2
After more tweaking, I was able to finally get my speeds stable. Your results may vary.
1.)Configure your actual network card in Win7
2.) Manually disable ANY “Offload” options and forcibly set your “Speed and Duplex” settings to the max speed on your network.