Andrew Brown asked about how to run Windows 3.1.
It is not too difficult, provided you have access to the install disks for DOS and Windows. An MSDN subscription will do. I tried Virtual Box with MSDOS 6.22 and Windows for Workgroups 3.11. Although it installed OK, it freezes if you use the mouse. Known bug apparently.
I tried Virtual PC instead. Microsoft wins this one: everything was fine.
I used the same procedure both times. It is slightly fiddly. I downloaded MSDOS 6.22 and WFW 3.11 from MSDN (subscription required). For some reason, the MSDOS you can download is an upgrade version. Therefore, I also downloaded a floppy image for 6.22 from bootdisk.com. This one is handy because it has a CD ROM driver. Note that my PC does not have a floppy drive. Here are the steps I used:
1. Make an ISO CD image including the WFW and MSDOS 6.22 files.
2. Boot a new VPC from the bootdisk floppy. FDISK and FORMAT /S to setup up drive C.
3. Mount the MSDOS 6.22 CD. Boot again from the bootdisk floppy. Copy setup files from MSDOS and WFW to C.
4. Boot from C. Run setup for MSDOS. Run setup for WFW.
5. Copy the CD driver and configuration from the bootdisk.
Since there is knowledge locked up in old, obsolete executables, the ability to run this stuff in VMs is reassuring.