I used legit keys with XP until it stopped accepting the one I was using. I needed a legit key to get the Service Packs, and I needed the Service Packs in order for it to read USB mass storage devices, so I Googled around until I found a guide on messing with the registry to make it prompt you for a CD key again, then used the CD key they had at the bottom of the tutorial.
I've never had that problem with running DOSBox on Vista. But you shouldn't actually need the slashes for anything other than quicker navigation. You can get there by simply doing cd progra~1, cd tlo, true_love95, etc.
