Assumption: you are running Windows 2000 TS on the server,
correct?
If you installed the TS CALs *before* the LS got SP3, then the
licenses have no expiration date and are permanently issued to a
specific client. You will have to phone the Clearinghouse to get
your license re-issued.
If your TS CALs where installed on the TS Licensing server *after*
installing SP3 (or at least SP3 + the post-SP3 Licensing
Enhancement hotfix), all TS CALs have an expiration date. That
means that a license which has not been used (a PC has not made a
connection to the TS) during a period of 52-89 days, will
automatically be returned to the Licensing server and become
available for another client. In the meantime, a new client will
receive a temporary license, which is valid for 90 days. So before
the temporary license on the new client expires, the old license
becomes available again.
If you find that new clients temporary licenses expire before any
old licenses are returned to the LS, it simply means that you
have, at least during some time, connected more clients than you
have TS CALs and you need to buy more.
For more information, see:
Windows 2000 Terminal Services Licensing FAQ
http://www.microsoft.com/windows2000/server/howtobuy/pricing/tsfaq
..asp