Scramdisk is a free on-the-fly encryption program for Windows 95, Windows 98, and Windows Me. A non-free version was also available for Windows NT.
The original Scramdisk is no longer maintained; its author, Shaun Hollingworth, joined Paul Le Roux (the author of E4M) to produce Scramdisk's commercial successor, DriveCrypt. The author of Scramdisk provided a driver for Windows 9x, and the author of E4M provided a driver for Windows NT, enabling cross-platform versions of both programs. Although Scramdisk's source code is still available, it was only released and licensed for private study and not for further development.
There is a new project called ScramDisk 4 Linux which provides access to Scramdisk and TrueCrypt containers. Older versions of TrueCrypt included support for ScramDisk.