On the 'System Requirements' page, Microsoft treats all Vista versions (with the exception of Vista Basic) as needing the same. The only part of Ultimate which has a unique requirement is the "Bitlocker Drive Encryption"
for which a 'TPM' chip is required, but not having a TPM chip doesn't mean Ultimate can't be installed. It simply means that feature won't be available.
http://www.microsoft.com/windows/pro...uirements.mspx
If you want to know what a TPM chip is, more info here:
http://www.msnbc.msn.com/ID/10441443/