This is a quick thread (to be expanded later). Some solutions may not work for everything:
MS-DOS
DOSBox
vDos and vDosPlus
nxvm
NTVDM64
winevdm/otvdm
How to run 16-bit/MS-DOS apps on 64-bit Windows
Re: How to run 16-bit/MS-DOS apps on 64-bit Windows
Reserved for future expansion