SmartDrive (or SMARTDRV) was a disk caching program shipped with MS-DOS versions 4.01 through 6.22 and Windows 3.0 through Windows 3.11. It improved data transfer rates by storing frequently accessed data in random-access memory (RAM).
Early versions of SmartDrive were loaded through a CONFIG.SYS device driver named SMARTDRV.SYS. Versions 4.0 and later were loaded through an executable file named SMARTDRV.EXE, which could be run at user's discretion or at boot time via AUTOEXEC.BAT. However, SMARTDRV.EXE also includes double-buffering driver that should be loaded through CONFIG.SYS. Version 4.0 also introduced 32-bit disk access and could reduce its footprint in conventional memory (the first 640 kilobytes of memory which was critical to MS-DOS) by running in upper memory area (the 384 kilobytes of memory located beyond the conventional memory).
A cloaked variant of SmartDrive utilizing the Helix Cloaking API was available from Helix Software. On Intel 80386 processors, it could run in protected mode to reduce its footprint in conventional memory.
Microsoft suggests SmartDrive to be used when installing Windows 2000 or Windows XP from MS-DOS to reduce installation time.