All these download files consist of extremely compressed empty disk images for emulators (such as SheepShaver or Basilisk II) that are to be used as hard drive to store files and/or the operating system. Once inflated, they will instantly take the whole space they are marked at. These empty disk images range from 3GB HFS formated (appropriate for Mac OS 6, 7 or 8.0) up to 32GB HFS+ formated (Mac OS 8.1, 9 or early Mac OS X).

Note: Please be patient when extracting these blank disk images, as your hard disk has to write the whole space (up to 30GB) so it might take a couple minutes depending on your computer specs.

HFS vs HFS+ quick tip from that-ben: Even tough HFS standard is highly compatible with almost all Mac OS versions, it still remains the worst choice for any Mac OS 8.1 or 9.x setup in terms of efficiency. The reason is the bigger the hard drive in standard HFS (not HFS+) is, the larger small files will use. For instance, think of a 30GB drive that you format as HFS standard (tough this would only be possible on System 7.5.2 or newer). Just a couple characters typed in a SimpleText document and saved on that drive will always result in a minimum size of nearly 1MB (1000000 bytes) instead of say, 8 bytes! This is due to the 16-bit blocks addresses limitation. The way HFS standard was implemented, there can only be limited small amount of blocks on a single drive, resulting in those blocks to distribute the hard drive space evenly and thus, be huge. Even if you write tiny files, the remaining bytes in those blocks are totally wasted, resulting in humongous files that contain next to no DATA. In other words, if you're planning on using, say more than a 10GB big drive in Mac OS 9, you should totally go with HFS+ as it will contain WAY MORE files than a same size HFS standard drive.

Note: For System 7.5.1 and older, the maximum usable size of a volume is 2 gigabytes. For System 7.5.2 and newer, the maximum usable size of a volume is 2 terabytes, but this is discouraged as it then renders those drives incompatible with previous versions of Mac OS.

Those are blank disk images, compressed. On Windows, you can use WinRAR or WinZip to extract them. On Mac OS X, you can use The Unarchiver.