DOSBox is an emulator which creates a DOS-like environment intended for running MS-DOS-based PC computer games which may not run properly on newer PCs and may not run at all on non-IBM PC compatibles (e.g. Macintosh). It also allows such games to be run on other operating systems that do not normally support DOS programs. DOSBox is open source and available for many operating systems, such as Linux, FreeBSD, Windows, Mac OS X, OS/2 and BeOS. Recently, it has even been ported to the GP2X  device.
DOSBox is a full CPU emulator, not just a compatibility layer like dosemu or the VDMs of Windows and OS/2, which rely on virtualization capabilities of the 386 family processors. It requires neither an x86 CPU nor a copy of MS-DOS or any other DOS to run, and it can run games that require the CPU to be in real mode or protected mode.
Graphics emulation: Text mode, Hercules, CGA (including composite and 160x100x16 tweaked modes), EGA, VGA (including Mode X and other tweaks), VESA and full S3 Trio 64 emulation.
Sound emulation: Adlib, PC speaker, Tandy, Sound Blaster, Creative CMS/GameBlaster, Disney Soundsource, Gravis Ultrasound, and MPU-401.
Network emulation: Modem simulation over TCP/IP, allowing for DOS modem games to be played over the internet. IPX network tunneling, which allows for old IPX Dos multiplayer games to be played over the internet. Finally, Win32 builds support direct serial port access.
Quick guide to DOSBox
After install prepare your game directory by simply create a dir somewhere on your hard-drive (use the root for an easier acces like c:\oldgames\) and unzip there all your favourites games each in his folder.
Start DOSBox and type (example) mount c c:\oldgames\ this will make a virtual dos drive then simply type c: and you’re there, however there’s often the case when you’ll put another game there and you should refresh the virtual drive index by pressing CTRL+F4 otherwise you’ll only see the old dir’s.
Where to get it
Download DOSBox (if you dont know what version do you need simply take the Windows one)