It's not a dual-core, it's a cheap and cheerful Dell Dimension B110
Please re-read my post. The 99% CPU usage occurs after psw32.exe crashes and an attempt is made to re-launch PS.
In that condition, PS does not launch completely, it stays on the splash screen, and stays there forever. CPU usage for psw32.exe at that time is 99% and would stay that way forever, also, if the process were not terminated. However, Task Manager can't terminate it -- the computer needs to cycled off and on again to end the process. This problem may be fixed in the latest software upgrade -- PS still only shows Channel B when the timebase is 200ms or slower, and it still crashes if I try to change any setting when the timebase is 200ms or slower, but PS does seem to be relaunchable without it hanging.
No other programs are having any trouble at all -- at least the ones we run on that box.
Right now I am trying to look at how a regulated voltage changes in response to Mains voltage variations. I need both channels to work, chart recorder mode, 1s/div timebase. All I get below 200ms is one channel, and PS wants to crash if I try to change any settings. None of these problems are occurring when the timebase is 100ms or faster.