SPC/AT Emulator (25.01.2013, Win/x86) - Performance boost, Covox support (Wolf3D etc.), 486 Award BIOS support.
Software BIOS, which included in emulator package, is not 100% PC/AT-compatible currently (yet workable in 99% of cases).
So (temporary) better to use configs with binary BIOSes, such as from Bochs x86 Emulator (supported by 586 config).
They can be found in Bochs installer (about 4 MB in size) (main BIOS file "BIOS-bochs-legacy" and
video BIOS file "VGABIOS-lgpl-latest" - last also can be found at it site http://www.nongnu.org/vgabios)
Real model configurations with binary ROMs mostly based on MESS collection of ROMs (romset).
With emulator can be used bootable FreeDOS floppy images ("freedos.img") or other bootable FDD/HDD images.
To import/export files to disc images shareware GUI tool WinImage exists (and other similar software).
Archive with empty hard disk images hdimages.zip (32-512Mb)