PCem emulates the following XT/AT-class PCs:
Acer 386SX/25N, AMI 286 clone, AMI 386 clone, AMI 486 clone, AMI PCI 486 clone (Shuttle HOT-433), AMI WinBIOS 486 clone, Amstrad MegaPC, Amstrad PC1512, Amstrad PC1640, Amstrad PC2086, Amstrad PC3086, Commodore PC30-III, Dell System 200, DTK XT clone, Generic XT clone, IBM 5150 PC, IBM 5160 XT, IBM AT, IBM PCjr, Schneider EuroPC, Sinclair PC200, Tandy 1000
PCem can be a bit time consuming to setup. You need to find roms (bios) for each system and install an operating system (in most cases). It can run most Windows systems (v1.0 - Windows 98) as well as DOS, old linux distros, and OS/2. If your willing to take the time this is a very fun emulator to play with.
Note: Most roms can be found in the MESS set (these are easier to come by). Also note that there are several generic roms available at PCem's website.