The last batch of KoF arcade games have been built on Taito's Type X² motherboards, which are based on various PC hardware configurations and natively run Windows XP Embedded. KoF XIII isn't the first arcade game in recent years to be pirated, but since Taito starting basing their hardware on Windows it's significantly increased the ease at which these games get ripped off.
You have to wonder why, if it's so easy for pirates to acquire, compile, and put out perfectly playable builds of quality arcade games, we're not seeing actual legitimate releases from the developers themselves. These games are built to run in Windows in the first place. No porting would be necessary, and the cost of arranging digital download of the games would be negligible compared to the profits they could potentially make. I know I'd certainly pay for a digital copy of KoF XIII, if it was compatible with USB arcade sticks and other controllers. SNK Playmore, what the hell?
