What's happening is that it's expecting the DLL to be somewhere other than where it's installed (ie in the main Palm folder). This is only supposed to happen if you've put the Palm folder somewhere odd, but it happened to me with the default C:\Program Files\palmOne location. Odd, and displaying a lack of QA by TomTom imo.
Reasonably easy to work around, although finding the answer was a bit more tricky. Kudos to Bertram Becker for
several workarounds and helpful screenshots, although it tested my German a bit.
The one that worked for me was to copy the following from the install CD into C:/Program Files/palmOne (or whereever you've installed the Palm application):
Folders:
* Licenses
* nvapps
* palmos
* rsc
Files:
* Setup.exe
* Resource CD.cid
Run Setup.exe from its new location and all should be well.