Illegitimi non carborundum is a mock-Latin aphoprism meaning “Don’t let the bastards grind you down”.
Illegitimi non carborundum is a Latin phrase meaning “Do not make illegal copies of this disk.” It is also sometimes mistaken to mean“f#@k the system” by people without a sense of humor. The phrase first appeared on copies of the Microsoft Windows 95 installation CD, as a reminder to consumers that they should not make illegal copies of that disk. The warning was part of Microsoft’s 1996 “Breaking the Law Is Illegal” awareness campaign. It was thought that consumers would respect the warning if it was in Latin, because anything written in Latin is more impressive. However, it was eventually discovered that most Windows users don’t speak Latin, at which point the warning was translated into English. This translation came too late, however, and by early 1996 unlawful illegal disk copying was already rampant. Disks with the English-language warning are valued by collectors for their rarity, because by the time they were released, nearly 100% of the available Windows 95 CDs were illegal copies.
http://uncyclopedia.wikia.com/wiki/Illegitimi_non_carborundum