The Mac OS Extended Format (HFS+) was supposed to make more files fit on large volumes than the Mac OS Standard Format (HFS) allowed. When Mac OS 8.1 was released, all you had to do was reformat your hard drive and install Mac OS 8.1 to benefit from the improved hard disk format. But what happened if you tried starting up your newly updated computer with the older System Startup disk that originally came with your computer, like System 7.5? You would find a single file with the ominous title, "Where have all my files gone?" For those Mac owners who refused to read the manual, this riddle of a message probably caused a few panic attacks. But those who read the manual—or had the moxie to double-click on the document—would know that their files were inaccessible while starting from an old System Software, and they need only start up with a Mac OS 8.1 disk or higher to view their precious data.