I use VMWare virtual machines for Windows development. In doing so, I've found in the past that when running Windows 7 in a virtual machine it's beneficial to use ReadyBoost to increase performance. ReadyBoost is the Microsoft technology built into Windows Vista and later, which allows you to plug in a ReadyBoost certified USB flash drive (memory stick) or SD card and use it for disk caching. This effectively speeds up the small, random reads from your hard disk, since long, sequential reads are faster from a hard disk.
The problem I had was that when my Windows Experience Index was calculated, the virtual hard disk was performing too quickly, and ReadyBoost was disabled by the system. I would open the properties panel of the USB flash drive and see the message below in the ReadyBoost tab.
This device cannot be used for ReadyBoost.
ReadyBoost, is not enabled on this computer because the system disk's performance is high, as measured by the Windows Experience Index Disk score. This computer would not benefit from ReadyBoost.
The Windows Experience Index didn't account for the fact that I'm in a virtual machine and disk performance varies wildly at times.
After searching high and low, and even trying to fudge my Windows Experience Index disk score, I found success by simply opening the "Services" MMC panel (in the Administrative Tools control panel), configuring the "SuperFetch" service to Autostart at boot, and then starting it manually. Once running, I was able to open the properties window for the USB flash drive and ReadyBoost was re-enabled.