I have been just getting the blank screens as well when trying EVR in WinXP SP2. Apparently nvidia is going to add EVR support for WinXP within a couple of months. I am trying to get confirmation from the nvidia forums.EVR in XP is possible, but MS doesn't support it officially and it also disabled hardware acceleration so it's not adviced to be used in XP.
I don't suppose there are any reg hacks for nvidia cards?