You could check your display

You could check your display manual to see what formats are supported. You could also check your display properties on your HTPC to see if the 23Hz and 24Hz options are available. They generally are not if the display doesn’t support those formats.

I haven’t played with the most recent iteration of TMT5, but there may be a configuration value that tells you whether the 24p capability is enabled. Your display may also tell you what input format it is receiving. You could also try checking the current display properties while content is playing back to see what the PC is configured for.