I'm running the SAP (large ERP system) IDES system on an XP SP3 virtual machine under vmware (on Windows 7 x-64).
This runs fine under vmware but -- don't even THINK of running this type of app in XP mode -- if it loads at all you'd be twiddling your thumbs all day long
Using vmware this stuff runs just fine.
XP mode is OK just for basic simple one off small applications and in cases where you want easy integration with your Windows 7 desktop without having to bother about Virtual networking etc etc.
Here's a screenshot of a SAP IDES system running in a Windows XP SP3 virtual machine under vmware. These types of apps don't run yet in 64 bit versions hence the need for the Virtual Machine.