Recently posted thread on the same subject:
This thread now marked as 'Expired'.
Taken from [ http://worthplaying.com/article/2010/8/9/news/76089/
'Modern Warfare 2' (ALL) Bug Grants Free SNK Games
by Adam Pavlacka on Aug. 9, 2010 @ 10:15 a.m. PDT
...Affecting both the downloadable demo as well as the full version game, the Modern Warfare 2 glitch grants players access to the full versions of five different SNK Xbox Live Arcade games.
The glitch works because all XBLA downloads contain the full version of their respective titles, even when you're just downloading the demo. After purchasing, the system simply registers the game to your account and the demo unlocks, granting you full access. Full version XBLA games can be tied to a specific console, a specific gamertag or even a specific type of media (such as in the case of compilation discs).
With Modern Warfare 2, the glitch forces the trial version XBLA games into thinking that they are authorized to run as the full version. As a result, they launch into the complete, unrestricted game, even if you have not yet purchased them. Oddly enough the glitch only seems to effect the combination of Modern Warfare 2 and the SNK developed XBLA games. Other titles tested behaved as expected.
In order to see the glitch in action, you only need to launch Modern Warfare 2. Once the game and/or demo has booted, press the Xbox 360 guide button and select "Quick Launch." Now, highlight the XBLA SNK demo that you want to play and confirm the selection. The XBLA game will launch as a full version.
The SNK games affected by the glitch are: Garou: Mark of the Wolves, The King of Fighters '98 Ultimate Match, Metal Slug 3, Metal Slug XX and Samurai Showdown II. Fatal Fury Special and NeoGeo Battle Coliseum are unaffected.
What makes this glitch so interesting is the specific nature of it and the fact that Activision's Infinity Ward and SNK have no obvious connection. We'll likely never know the root cause of the glitch, and expect it to be patched shortly, but for now Xbox 360 owners around the world can get their fight on, free of charge, thanks to Modern Warfare 2. Makes you wonder if SNK will be sending Bobby Kotick a bill for lost sales?...