ReadyBoost is a new feature included with Windows Vista that allows you to use a flash drive to improve system performance without having to add physical memory to your computer.
ReadyBoost was included with Windows Vista to allow the use a USB flash device to act as memory cache. This allows applications to use the flash drive for additional memory when the physical memory is used up. Accessing flash memory is much faster than using the hard drive as Virtual Memory.
ReadyBoost relies on the SuperFetch memory management system in Windows .
Not all flash drives can utilize the ReadyBoost feature. Make sure the flash device indicates it is ReadyBoost Compatible.