Writing to a hard drive is not as quick as writing to a flash drive. Somebody at Microsoft decided to see about making that simple fact into a new feature and so now we have ReadyBoost. The way it works is that you can tell Vista to use a USB drive to cache data that would otherwise need to be ready from the hard drive. Another Vista technology, SuperFetch, is used to determine which data should be cached.

If you insert a USB flash drive or SD card greater than 256 meg, Vista does a very quick check to see if the device is fast enough to work with ReadyBoost. If it is fast enough, you'll have the option to enable ReadyBoost, or you can go into the drive properties and check the ReadyBoost tab. By default, the same device will not be checked twice, but you can control that from this tab (and you can have it retest by hitting the "Test Again" button).

When ReadyBoost is in use, you should see a performance gain in the startup of applications. This can be particularly helpful in a notebook situation, but you probably don't want a USB stick hanging out of your computer if you are moving it around. If you are lucky, you'll have an SD slot you can plug into so it will be completely out of your way.

If you are using it, don't worry about pulling out the memory-- this action will automatically disable ReadyBoost and you don't need to worry about loosing any data of value as this is just temporary copies of data that you do not need to be concerned about.