1.91 is the "official" patch right now. 1.92 is officially beta, although i do recommend it. Plus, you can only play on 1.92 servers if you have 1.92 installed.
1.93c is really inofficial and is only for debugging purposes. You can play with 1.92 on 1.93 servers. Unless you experience ctd or networks timeout really often you should not install 1.93c.
Oct 4 2003, 15:56
1.93 has not been made available on general release.
Please do not PM or Email me directly about your CD Key issues, follow the guidance in this thread instead.