The key to this is to be aware that the license servers <5.0.81 cannot license a client >=5.0.81 and vice-versa.
Also, if you have TRIED to install a version older than 5.0.81 onto windows 2000 or XP you will probably have to check out this thread:
http://yabb.jriver.com/ice/index.php?board=2;action=display;threadid=210 to fix that client PC.
As long as you don't touch the existing clients you can install an updated server over the top of your existing server. If for any reason, you need to rerun configwizard on the old client PC's after the server upgrade you will have to rerun the install on that PC to update that client because versions NEWER than 5.0.80 cannot give a sequence number to older versions.
Purchase an update.
to the licenseadmin server machine. Next backup the license and data folders to some removable media:
Program Files->J River->ICETCP5 Server->TCP5_USER->Licenses and
Program Files->J River->ICETCP5 Server->TCP5_USER->Data
Run the SERVER install and license admin. When licenseadmin comes up, check to make sure your licenses and users look ok. If not, exit licenseadmin and copy your backups in place of the licenses and data folders listed above and rerun licenseadmin. When everything in licenseadmin looks good you can go on to install PRO onto new client machines or update existing ones.
If you are moving the licenseadmin server to a new machine and updating a version older than 5.0.81 at the same time, the procedure above is the same EXCEPT that you install the update onto the new machine and put the license and data folder backups you made from the old machine onto the new machine in TCP5_USER. When licenseadmin looks good on the new server, delete the licenseadmin server on the old machine by deleting the admin portion (to prevent future sequence number conflicts). Just dump the ICETCP5 Server folder in Program Files->J River into the recycle bin.
Make sure your TCP5_USER share on the licenseadmin machine is shared FULL CONTROL for everyone.
From a client PC, BROWSE to the TCP5_USER share on the licenseadmin machine and run the setup.exe in there. When you get to the configwizard portion, uncheck the "Select a configuration profile" box on existing client PC's. Leave it checked on new client PC's.
If you run into sequence number problems after this it's likely that your licenses were out of sync before and the addition of new client PC's has caused conflicts. If this occurs you should delete all of the users in licenseadmin and update all of your old existing client PC's to the current version via the process above and rerun configwizard on the newly installed PC's.