Then he is an official seller (most probably), ya u can't register anymore, read the cabalrider discussion thread. Just create a CR account and wait until u get your code.
I don't think that this guy is an official seller, go to cabalrider.net to search for the sellers or ask in the cabalrider discussion thread. And use the search function, you can find all the things you need in the release sections..
Take your anti-virus and firewall off meanwhile you use CR. If you still can't use it try the usual, uninstall CR -> run ccleaner -> reinstall cabal -> try it. Btw CR isn't support 64 bit systems u might need to install win xp or win vista 32 bit.