Hi Paul, welcome to the forum!
The solution may lie in one of the following four sets of steps (this is item 11 from the link below):resources/faq.html
Solution 1: Run NVIDIA System Monitor (Start -> Programs -> NVIDIA Corporation -> NVIDIA System Monitor) right after a restart. You should only need to run it once for the Performance option to (hopefully) appear.
Solution 2: (which it sounds like you've already tried) Failing that, try uninstalling and reinstalling the ESA software.
Solution 3: If that doesn't work, try the following steps:
A) Disconnect the power molex (item no. 6 in the following link) from the Master I/O Board situated behind the case fan housing (link with photos here--see billybigfoot's second post on this page).
B) Shut down your PC and disconnect the power lead/connector, then press the power button to discharge any residual power.
C) Open the case and you will be just about able to get to the molex connected to the Master I/O Board fixed to the inside of the case to the rear of the upper fan. Unplug it.
D) Reconnect your power lead/connector and restart your PC. Let it boot to the desktop, and then shutdown again.
E) Disconnect the power lead/connector once more and press the power button.
F) Reconnect the molex to the Master I/O Board. Replace the power lead/connector and restart.
Solution 4: If these three steps still haven't resolved it, it may mean a bad Master I/O Board in need of replacement.