EmuNations

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..

DiscCheckEmu is a tool designed to emulate disc checks found in many disc-based games and software without the need for physical media. By intercepting API calls and modifying their behavior on the fly, DiscCheckEmu provides a seamless experience for users looking to enjoy their favorite legacy software without the hassle of keeping CDs or ISOs mounted.

As computers increasingly lack CD-ROM drives, accessing old disc-based games and software has become impractical. DiscCheckEmu addresses this issue by allowing users to emulate disc checks, enabling them to run their favorite titles directly from their hard drives, without physically patching the game executable.

Please note that DiscCheckEmu works only for games and software that employs standard disc checks: old disc-based protections like SafeDisc, SecuROM or LaserLock are not (and will not be) supported by this software. This is due to the nature that these protections that use segment encryption and IAT obfuscation.

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. 

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... 

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.

VirtualBox is a powerful x86 and AMD/Intel64 virtualization solution for home and enterprise usage. It's quite feature rich, high performance yet is freely available as an Open Source Software. While it's mainly a community effort, Oracle is backing it to ensure it maintains high standards of quality.

Presently, it runs on Windows, Linux, Macintosh, and Solaris hosts and supports a large number of guest operating systems including but not limited to Windows (NT 4.0+, DOS/Windows 3.x, Linux (2.4, 2.6, 3.x and 4.x), Solaris and OpenSolaris, OS/2, and OpenBSD.

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