assuming your running F@H under FireDaemon ... you say its a service ... the absolute foolproof way is:
1 - Download new client (
3.25 ).
2 - Stop the service in Firedaemon or whatever..
3 - either:
a - delete old client and rename/move new client to where the old one was
or
b - reconfigure Firedaemon with the new client.
The core will be the same (78 for Gromacs or 65 for Tinker if im not mistaken) but the new client will force SSE instructions if you use the -advmethods tag when you run it ...

simple no?