After changing the network adapter type on a VMware virtual machine from NAT to bridged, the transfer speed from shared network folders dropped to about 25 kb/s and browsing shared folders was really sluggish. The network folder was located on the host machine, which was running Windows 7 Searching the VMware knowledge base resulted in the following article. I can confirm that the proposed solution also applies to Windows 7:

Performance issues with bridged networking on Windows Server 2003 and Windows 2008 host operating systems

In short: Use regedit to navigate to the following place:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

Then create a DWORD key named DisableTaskOffload and give it ‘1’ as value. TCP task offloading means distributing calculations concerning the network communication to the network card, so creating this registry key means that all these calculations will be done on the CPU.
Microsoft Virtual Server seems to be susceptible to the same problem and offers the same solution along with two others: Slow performance when you try to access resources on your Virtual Server 2005 host computer from a guest virtual machine