I had a quick look at the readme.txt for tracetcp. It mentions the following:
If you need to use the program with a dial-up connection then you can revert to the old raw sockets interface by using the -R switch (this will not work with XP sp2 of course)

As luck would have it, I'm on dialup and am using XP with service pack 2 installed.

I've got a spare hard drive lying around so I'll stick an earlier version of XP on it (prior to sp2) and try tracetcp with the raw sockets interface. It might be a few days before I report back to this forum on how everything goes though.

Thanks again.