All Divx discs have a Divx title, and they apparently have a series of deliberate errors that Divx-compatible players use to identify the format as Divx-format. There is a small file on the disc in standard format, while the Divx format uses a different CRC algorithm that makes regular players and computers think that the data is all corrupted or just trash. DVD players (including personal computers) will run the stub file instead, which displays a screen informing the user that the disc must be used in a Divx-compatible player.

It's possible to "unlock" a Divx player for play past the decommission date, but Circuit City decided not to provide this feature to Divx owners. Unlocked Divx players were made available only to certain high-ranking Divx and Circuit City employees.

A patent lawyer advised me that anyone producing a software player might be subject to prosecution under the federal DMCA legislation.

I've heard of a semi-hack for players. It involved disabling the player timer, except for the first few seconds of a disc starting up. However, it can not be used indefinitely, as the player's memory will eventually fill up. Also, the semi-hack had to have been performed prior to the expiration of all Divx accounts on July 7, 2001.

A patent lawyer advised me that anyone producing a software player might be subject to prosecution under the federal DMCA legislation. Besides, at the moment it is technically unfeasible. Unless a set of the decryption keys became available somehow, writing a software player would require calculating the decryption key for each and every disc, something that can't be done with current technology. It would take either a massive increase in computing power or big advancements in algorithms for breaking encryption.