As a rule of thumb you should always update your licence server with each version release...
However ST4, ST5 and ST6 all use the same LM.
Can you provide any more detail about not being able to install the LM from ST6. Any specfic error messages or such.
Truth be told, ST6 will now allow us to run dual install, though this has it's own unique set of challanges and things that need understood. I just bring this up to confirm that ST5 and ST6 can and do run on the same LM.
Note your Client install default path for the licence file has changed. We are now storing the license file in the "Preferences" folder C:\Program Files\Solid Edge ST6\Preferences
Well, I tried to re-install ST5. My Server is still giving the same message "non-supported operating system" . The message also includes the systems that ST5 can be ran on (2008 and XP), but does not include Windows 2003. I searched the information section on the cd and it lists 2003 as compatible. Any suggestions?