Here is an interesting Q&A session on the MSDN site relating to how Windows Vista Readyboost works. ReadyBoost is a technology that improves small random reads from the hard disk. These random reads are particularly hard on slow hard disk drives. Readyboost uses a cache file on a USB flash drive to improve the performance. Flash memory drives have very quick seek times, often less than 1ms. For small files that are frequently accessed this reduced seek time improved read performance. The article is written by one of the Microsoft MSDN MVP leads. Readyboost has been improved greatly for the Windows 7 OS, but for the Windows Vista Operating system it provides a nice speed boost for older computers.