For my old school needs I use the following...
Dosbox on a modern quad core rig.
Dos 6.22 original factory install on a Gateway P5-90
Win 98SE on a P2 400mhz (for the few Win 95/98 games that wont work right on XP)
I find that almost everything runs perfect in Dosbox anymore, so I dont use the dedicated machine as much. But its good to keep around for the rare few that just wont work.