I'd like to suggest taking a look at your Network adapter. Start -> dev manager -> network adapter. Double click, open her up and then under "advanced", take a look at "Link Speed & Duplex".
If this is set to auto-negotiation, try re-setting it to 10 or 100mbps Full Duplex, re-start your computer and see if the problem persists.
For whatever reason, auto-negotiation features in some network cards poor. Also, if you haven't, undo the reserved ip (static) that you set up for you Windows 7 box before you change this network card setting.