MAME stands for Multiple Arcade Machine Emulator. When used in conjunction with an arcade game's data files (ROMs), MAME will more or less faithfully reproduce that game on a PC. MAME can currently emulate over 2600 unique (and over 4600 in total) classic arcade video games from the three decades of video games - '70s, '80s and '90s, and some from the current millennium.

Intel Celeron / AMD Duron 700 MHz
64 - 128 MB RAM
a varying amount of hard drive space (a full MAME ROM set would take over four gigabytes, but most individual ROM sets are quite small)
DirectX (Windows version) or VESA 2.0+ (DOS version) compatible graphics card
Any sound card that works in Windows (Windows version) or Sound Blaster compatible sound card (DOS version)

Head on over to the official site for the DOS version, Pentium Pro version, and the Source.