There are many questions about which versions of Microsoft Project and Microsoft Project server are compatible. Here are the general rules:
Project 2000 connects to Project Central
Project 2002 connects to Project Server 2002
Project Professional 2003 connects to Project Server 2003 and Project Server 2002
Project Professional 2007 connects to Project Server 2007
No other connections are possible.
Project 2007 was redesigned in a number of ways to make it more efficient and improve performance. These changes included changes to the database schema and to the method that data is transferred. ODBC was abandoned in favor of Web services. This means that compatibility between the two versions was broken completely
One nod that Microsoft made to ease the pain was that they did make it possible to install the 2003 version and 2007 version side by side on the same machine. This applies to both Project Professional and Project Server.
It is important to note that Project 2003 knows nothing about 2007 so you should always install 2003 before you install 2007 or 2003 may overwrite the 2007 installation or do other bad things.
Project 2007 can read from all versions back to Project 98, but can only write back in Proj 2000 or later. It can read from ODBC but not write back to it. This means that any .mpd databases will have to be converted to stand-alone files or stored in Project Server if you want to continue working with them.
