Remember when installing a PC game meant putting a physical disc into your computer? In 1996, id Software tried to make the most of that format with an unusual Quake shareware CD-ROM that packed far more than just the game onto the disc.

As detailed by game programmer and historian Fabien Sanglard, the Quake shareware CD used only around 22MB of a 640MB CD-ROM, leaving an enormous amount of unused space. Rather than waste it, id Software came up with an ambitious plan: the disc would contain locked versions of the company's entire game catalog.

The concept was designed for an era before modern digital storefronts and widespread high-speed internet. Players could purchase the relatively inexpensive shareware CD from a retail store, then call a dedicated hotline to pay for individual games. After making a payment, the customer would receive an unlock code that could activate the corresponding game already stored on the disc.

It was an inventive idea, but there was one major problem: the protection system was far easier to crack than id Software anticipated.

Just 39 days after the CD launched, a program called Qcrack.exe appeared online. It allowed users to generate the serial numbers needed to unlock the games without actually paying for them.

The system worked by having the CD's interface generate a code that would normally be given to a phone representative. After payment, the representative supplied a serial number that the unlock software would check against the generated information.

Unfortunately for id Software, the software running locally on the user's computer was capable of generating a valid serial number itself. The program essentially needed to confirm that the generated and entered numbers matched, meaning hackers could reproduce the process without contacting the unlock center at all.

Suddenly, a cheap Quake shareware disc could potentially provide access to id Software's entire catalog, including the full version of Quake and numerous other games.

The situation became even more embarrassing because legitimate customers occasionally encountered problems that pirates didn't.

Sanglard discovered several errors inside the CD's file structure, including a typo that prevented Final Doom from being properly unlocked through the official system. A capitalization mistake meant the unlock process looked for the wrong file, creating the bizarre situation where an unauthorized copy could actually provide a smoother experience than the legitimate purchase.

The commercial consequences were significant. According to an account cited from David Kushner's Masters of Doom, id Software eventually found itself sitting on nearly 150,000 unsold CDs after the scheme spiraled out of control.

The experiment demonstrates just how different game distribution was in the mid-1990s. The idea of shipping an entire library on a single disc was remarkably forward-thinking, particularly at a time when downloading full games over the internet was impractical for most players.

Unfortunately for id Software, the company also discovered an equally important lesson: putting all your games on one disc is only a great idea if the lock protecting them actually works.