Hyper-V Program Manager
During the development of Virtual PC 2004 - our primary focus was to perform a thorough security review of the entire product (After which - I have nothing but respect for the level of commitment that Microsoft now has to shipping secure products). Unfortunately - some of the changes made as a result of this review did negatively affect some areas of Virtual PC.
One area that did get affected by this was the performance of IPX based networking under DOS virtual machines. However, there is a simple solution for this - don't do that :-)
Well - for a bit more clarification; most DOS programs can run perfectly well under Windows 95 / Windows 98, and both Windows 95 / Windows 98 supported IPX 'out of the box'. If you have a DOS program that needs IPX networking - and you find the networking performance to be unacceptable - you can resolve this by setting up a Windows 95 virtual machine with IPX enabled. Your DOS program can then use the Windows IPX network capabilities - which are significantly faster under Virtual PC 2004.