2009a and Windows 7 are generally compatible, for specific processors. If you are not using one of those processors, then possibly making the adjustment is possible. The first step is to turn off the Windows Areo feature -- you cannot count on full Areo support back then.
If you have problems beyond that then you should be contacting Mathworks technical support for free installation help.
Windows 7 Ultimate is not considered a server system, but it has some server capabilities that are not present in the least-expensive Windows 7 version.
It might help to describe specific problems you are encountering, as someone might recognize them.
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