HKEY_LOCAL_MACHINE->SOFTWARE->Mercury Interactive->QuickTest Professional->Logger->Media->Log.
When you run a test, the results folder that is created by QTP will now contains a Log folder too. This will contain LogFile.html, which will be the HTML version of the report.
Source: http://forums13.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1231412262014+28353475&threadId=1222546