Slow network file copy on Windows 7

Question

I wrote a program that uses xcopy to transfer files (usually between 1KB and 2MB) over our intranet. Usually, I am copying files from my host machine (Windows 7 x64) to a VMWare virtual machine running Windows Server 2008 (the VM is running on my host machine, if that matters).

On Windows XP, the file transfers usually only require a few seconds to complete. But on my Windows 7 machine, the transfer of the first file (1.5 MB) takes around 1.5 minutes to complete. This is true whether I use xcopy, robocopy, or programmatically using File.Copy(). I noticed that if I use File.Copy, the first transfer is very slow and subsequent transfers are much faster.

Any clue how I can speed up the process? Is there a setting in Windows 7 (or server 2008) that I could try?