Touch HD runs Win Mobile 6.1; it is a similar device to my HTC TyII, but higher specified (say, more RAM and faster CPU). My device run CoPilot(that came with it) and Tomtom Explorer (which I bought earlier for another device) without any issues. I think you wouldn't have any problems either on your PDA.
I have recently bought an HTC Touch Diamond 2 which basically is the same as HTC HD except for it's size. Tomtom 6 is working very smoothly on it without any hassles.
I have a HTC Touch Diamond with preinstalled tomtom Navigator 7.
After talking to a TomTom customer support I have bought and downloaded a map from them. It appears he sold me old version 6 maps (will not work on version 7 software).
If you buy the wrong map from their website, TomTom will not provide a refund despite their bad advice.
My HTC Touch 2 (09) with built in GPS runs great with Tom Tom navigator 7
Maps are great no hicups here in Australia
I found my Garmin XT Mobile wouldn't use the internal GPS and the external was so slow
so went to TOM TOM
TomTom have released verions specifically made for these phones. Tomtom6 for the Diamond, Touch Pro, etc, ones running WM 6.0, 6.1. Tomtom7 is for the newer ones running WM6.5 though you have to get the right maps, not all work (ie, I had to get the 2883 maps because it wouldn't recognise the 2884).
Only problem is that tomtom doesn't rotate when you flip your phone, I believe Garmin does, so it depends on which view you prefer.
My HTC Touch 2 (09) with built in GPS runs great with Tom Tom navigator 7
Maps are great no hicups here in Australia
I found my Garmin XT Mobile wouldn't use the internal GPS and the external was so slow
so went to TOM TOM
This is strange... I have both TomTom Navigator 7 and Garmin Mobile XT on my HTC Touch 2, and they both work well (also with the POI downloaded here )
Have you downloaded the QuickGPS to speed up the time for satellite search?