The Multiple Arcade Machine Emulator (MAME) is software which makes a PC (and other computers) behave exactly like various coin operated arcade games. The following technique allows you to slow down many compatible games, making them more playable for people with slower reaction times:
Some games have more than one CPU (Central Processing Unit - or brain), but usually CPU0 is the right one. Slowing down the processor can give strange effects with certain games, so experiment until you get satisfactory results.
If this doesn't work, there is an alternative method that seems to work with all games, using a utility that slows down your entire PC at your control. You will need to go into the advanced properties of the game you wish to slow down, then set "Frame Skipping" to "Draw Every Frame". You will also need to switch off the technical features "Match game refresh rate", "Sync monitor refresh" and "Wait for vertical sync".
Arcade: MAME or MAME32QA with legal games from StarROMs and slightly dubious games from Rom-World.com. Add cheats to make play easier via Pugsy's MAME Cheats.
Atari VCS/2600: "Stella" with games from AtariAge.com
Commodore 64: CCS64 with games from c64.com and gb64.com
For help obtaining or using this system, please e-mail.