Diablo Spawn is the share ware version of Diablo, a 1997 computer game made by Blizzard, the makers of the Warcraft and Starcraft franchises. Blizzard also created World of Warcraft in 2005.
Basically, way back when LAN parties were cool and MMORPG's were still very early on in their evolution, one would install Diablo Spawn on their friends computers, then run an online play with them while using the ACTUAL Diablo to run the operation.
Diablo Spawn comes free with the Diablo CD, which you can find in the Diablo Battle Chest, for 30 bucks at Walmart. If you want a bit of late-1990's retro action, then buy it and play your troubles away.
Greg installed Diablo Spawn on Mike's, Jordan's, and Eric's computers, so he could play it as an MMORPG with his friends, without them having to buy the game separately.