The command to get a performance counter to recur on a set daily schedule under Windows Server 2000 and 2003 is:

logman update yourlogname -b 08/12/2008 23:00:00 
    -e 08/13/2008 09:00:00 -r

So the -r at the end causes it to recur on every date after 8/12-8/13 in those same hour windows (8/13-8/14, 8/14-8/15, et al.).

Server 2008 of course allows you to schedule the logging via the GUI.