EmuNations

QEMU is an open source machine emulator and virtualizer.
When used as a machine emulator, QEMU can run OSes and programs made for one machine (e.g. an ARM board) on a different machine (e.g. your own PC). By using dynamic translation, it achieves very good performance. 

Steam Rom Manager is a bulk game importer and artwork manager for Steam. It's basically an app for managing ROMs and benefiting from what Steam has to provide. This includes using big picture mode, its overlay, controller management layout,  streaming options and much more..

dgVoodoo is a wrapper for old graphics APIs to run on modern Windows operating systems. Its applied using Direct3D11 with different types of wrapping outputs:

• Hardware rendering at GPU feature level 10.1 (recommended)

• Hardware rendering at GPU feature level 10.0 (there are some restrictions)

• Software rendering through Microsoft WARP renderer

The API's it currently can wrap are:

• Glide 2.11, Glide 2.45, Glide 3.1 and Glide 3.1 Napalm

• DirectX 1-7 (all versions of DirectDraw and Direct3D up to version 7)

• Direct3D 8.1

You also need the 3Dfx splash dlls for Glide if you want 3Dfx splash screen or watermark (shameless plug) through dgVoodoo. 

• 3DfxSplashDlls.zip

You may also need D3DRM.dll (Direct3D Retained mode) for some games and demos. It's not part of the OS since Windows Vista.

• D3DRM.zip

Playnite is an open source video game library manager with support for 3rd party libraries like Steam, GOG, Origin, Battle.net and Uplay. While providing one unified interface for your games, it includes game emulation support, fullscreen mode, themes and much more.

Requires Windows 7+ and .NET Framework 4.6 

Wine (Wine Is Not an Emulator) is a compatibility-layer capable of running Windows applications on several POSIX-compliant systems such as Linux, macOS & BSD.

Instead of simulating internal Windows logic like a virtual machine, Wine translates Windows API-calls into POSIX-calls on-the-fly, thus eliminating performance and memory penalties and allowing you to cleanly integrate Windows applications into your desktop.

WineD3D For Windows is a DirectX 1-11 to OpenGL wrapper with almost full implementation of DirectX used in Wine. Even if Windows supports DirectX natively, using WineD3D can enhance backwards compatibility with older games, especially on Windows 8+ that don't support 16-bit screen modes. Others possible values include eliminating unsupported versions of DirectX, or porting DirectX applications to OpenGL without having to rewrite the rendering code. That said, it's far from perfect... 

DOSBox-X is a free and cross-platform DOS emulator for running DOS games and programs. Started as a fork of the DOSBox project, it retains compatibility with the wide base of DOS games and DOS gaming DOSBox was designed for. But it's also a platform for running DOS applications, including emulating the environments to run Windows 3.x, 9x and ME and software written for those versions of Windows. DOSBox-X aims to be a complete DOS emulation package that is both fully-featured and easy to use, covering all pre-2000 DOS and Windows 9x based system scenarios. 

While they have made efforts to maintain and improve the emulation accuracy of the hardware and many more ways to configure the DOS virtual machine, they also try to strike a balance between emulation quality, speed, and usability, including improving the out-of-the-box experience for new users who want to run DOS programs or games, as well as implementing emulation that is accurate enough to make retro-programming possible with confidence the program will run properly on actual hardware.

MS-DOS Player is a MS-DOS emulator running on Windows (32/64-bit) command prompt. Its 16-bit MS-DOS compatible commands can be executed on Win32/x64 environments.

It basically inherits the environment variables from the host Windows, and a target command can access the host's file path directly. As such, you can execute 16bit MS-DOS compatible commands on your 64bit Windows in the same sence as you did on 32bit Windows, and you do not need to copy any files to/from a virtual machine (VMware, Virtual PC, XP mode, or others).

Note: This emulator DOES NOT support Win16 execution files. It aims to support character user interface utilities, for example file converters, compilers, assemblers, debuggers, and text editors. For now, doesn't support graphic/sound hardwares nor is intended to support game softwares.