Adding system memory (typically referred to as RAM) is often the best way to improve a PC's performance, since more memory means more applications are ready to run without accessing the hard drive. However, upgrading memory can be difficult and costly, and some machines have limited memory expansion capabilities, making it impossible to add RAM.

Windows Vista includes Windows ReadyBoost, a concept in adding memory to a system. You can use non-volatile flash memory, such as that on a universal serial bus (USB) flash drive, to improve performance without having to add additional memory "under the hood."

ReadyBoost is present, with fewer restrictions than in Vista, in the beta version of Windows 7.

The flash memory device serves as an additional memory cache—that is, memory that the computer can access much more quickly than it can access data on the hard drive. Windows ReadyBoost relies on the intelligent memory management of Windows Superfetch and can significantly improve system responsiveness.

It's easy to use Windows ReadyBoost. When a removable memory device such as a USB flash drive or a secure digital (SD) memory card is first inserted into a port, Windows Vista checks to see if its performance is fast enough to work with Windows ReadyBoost. If so, you are asked if you want to use this device to speed up system performance. You can choose to allocate part of a USB drive's memory to speed up performance and use the remainder to store files.             

Getting ReadyBoost set up and working on a Windows Vista computer is extremely simple. First, insert an empty USB drive into the computer's USB2.0 slot and Windows Vista will do a quick test to make sure the device is ReadyBoost compatible. It's a good idea to move all your data off the USB drive before setting it to function in ReadyBoost.

The AutoPlay window should pop up, if not open up "My Computer" then right click on the USB device and go to "Properties". Click the "ReadyBoost" tab. From there check the "Use this device" radio box and then use the "Space to reserve for system speed:" slider to assign how much space you want to assign to ReadyBoost. Once that's done click "OK" or "Apply" and you're set!