Apparently they aren't named as ReadyBoost:
Quote from the web page:
"Vista's counters are named:
Hit read bytes/sec
Invalidated update buffer blocks/sec
Invalidated update buffer bytes/sec
Keep in mind, that in both Windows Vista and Windows 7, Performance Monitor will
not display the ReadyBoost Cache counters unless you have a device connected and
configured to use ReadyBoost.
In other words, if you are not using ReadyBoost, Performance Monitor doesn't show
the ReadyBoost Cache counters. "