I know MSDE is no longer supported on Vista, is this also the case for Windows Server 2008?
The status is the same for Vista and all OS after Vista, which includes both Windows 2008 and Windows 7.
I do not know if you can somehow "make it work", but you will not get any Support from Microsoft.
Edit: Source is here, the two important bits:
MSDE 2000 will exit mainstream support on 4/8/2008 and no new deployment agreements will be allowed after June 30, 2007.
and
Yes, MSDE will be supported through the end of it's life cycle on the operating systems it is currently designed to run on.
(That was up to Windows XP and 2003 Server)
Just to have this on the question for reference...
MSDE has been supplanted by SQL Server Express (same idea), which does run on Vista/2008. Links are:
It should be known that there are some significant differences between SQL Express and MSDE. While a number of these differences are in the favor of SQL Express we found that the critical items for us were the ability to run as a publisher which only MSDE supports as well as the lack of a SQL agent in Express.
For an excellent side by side comparison see:
http://www.microsoft.com/technet/prodtechnol/sql/2005/msde2sqlexpress.mspx#EKE