Windows Vista introduces a number of new technologies, among them one called Windows ReadyDrive that works in conjunction with new hybrid hard drive technology to improve the performance of your PC. Windows ReadyDrive makes use of non-volatile flash memory now being included on board these drives to give the OS an advantage in terms of both all-around performance and battery life.
The new hybrid drives, expected to be in market later this year from partners such as Samsung and Seagate, are equipped with integrated non-volatile flash memory, enabling them "spin down" for longer periods of time -- thus increasing battery life for laptops. Also, performance-critical data is loaded into the flash memory so that the hard drive is referred to less often, thus boosting system responsiveness. Lastly, the technology enables shorter boot times when specific boot files are loaded into the flash memory, so that cold boots, restarts and resuming from sleep or hibernation is faster.
Windows ReadyBoost is a technology native to Windows Vista, and so is not retro-fitted to other operating systems. You'll find more information about it and its interaction with the new hybrid drives in this whitepaper (Word format).
News source: Windows Vista Team Blog