I agree, and should have mentioned VPC2007,,, but as stated I think the OP is looking for Win2000 Mode.
I do not think that you can use Win 2000 like you can XP Mode. It is strictly XP mode... but again,,, VirtualBox has a similar mode that might work with Win 2000.
Win2k Main Stream Support did end in 2005 and Extended Support ends 7/13/2010
Meaning that if they had any ideas of implementing a W2k type XP mode in 7, they would not, due to the main stream support has already ended. Extended Support only relates to needed updates. Other than that, no development from MS is being done at all in regards to W2k.
This is also true for XP as Main Stream Support ended 4/14/2009 (unless there is some unofficial extended main stream support...