Some USB keys are fast enough for Ready Boost, yet Windows Vista will tell you otherwise. If you want to brave it and force Windows to use your USB key with Ready Boost, try these few steps.
1. Insert your USB Key. Right Click the USB key in “My Computer”. Click on ReadyBoost tab.
2. Check the box “Stop retesting this device when I plug it in”.
3. Unplug your USB Key.
4. Go to Start | All Programs | Accessories | Run. Type “regedit” without quotes.
5. Navigate to HKLMSoftwareMicrosoftWindows NTCurrentVersionEMDMgmt
6. Select the key related to your USB Device
7. Change the Device Status to 2, ReadSpeedKBs to 10000000 and WriteSpeedKBs to 10000000.
8. Plug the USB key back in, right click on it in “My Computer”, open the Properties page, ReadyBoost Tab, and
click “Use This Device”.