Could anyone explain the differences between AMD's 939 and 734 sockets?

(making a dedicated server the the LAN parties!)

Any help would be appreciated.

Socket 939 is the socket of choice for high-end AMD CPU's, like the Athlon64 and 64 FX. Besides the higher-end chipset/mobo implications, 939 also has the advantage of supporting dual-channel RAM. In practical terms, 939 is more expensive, but is better for upgradability (NForce4 is 939 only, and future A64/FX CPU's will be 939 versions).

Socket 754 is the value-oriented version, and is home to both the upper Sempron line (Socket A Semprons also exist) and the lower Athlon64's (no Winchester core on 754). There's only single-channel RAM support built into Socket 754, and there hasn't been a new chipset release for 754 in a long time (NForce3 and K8T800 are still your only options) which means you have to settle for AGP only, less SATA ports (no SATA 2.0 support), less USB ports, etc.

While I would highly recommend Socket 939 for a gaming system if you can at all afford it, Socket 754 would be perfectly fine for a dedicated server. Servers in general benefit from lots of CPU power, lots of RAM, and lots of storage, and do not necessarily require the absolute best system performance. For most games, even the CPU power available to a Sempron 2800+ would be more than enough (Semprons are cheap, tho, so a 3100+ wouldn't be much more), but I would recommend at least 1GB of RAM (again, dual-channel is not necessary) because you never know what game you'll be hosting or how many players. Also, there are several SATA 1.0 hard drives that have NCQ, so SATA 2.0 ports are not necessary for getting high-end hard drive performance. For HDD size, I would recommend at least 160GB since that's so darn cheap now, but NCQ versions are usually 200GB+ in size. A vid card is totally unnecessary for a server, so onboard video is plenty (or a cheap $50 vid card if you want to have all RAM available). For the OS, I would recommend WinXP Pro or Win2k Pro, since those OS'es both have advanced networking options, which come in handy for a server! :p Or if you're playing some of the latest games, Linux is also an option. Most of the latest A/B-list games offer Linux versions of their dedicated server.

Any more questions?