In Windows Vista, a problem may occur where the Hibernate option is grayed out. This could happen if your system doesn’t support the Hibernate feature, or doesn’t have enough hard drive space to save data during hibernation. Try these steps to enable the Hibernate option.

1. Click the Start orb and type command in the Start Search box.

2. Right-click Command Prompt in the Programs list, and click Run as administrator.

3. Click Continue on the UAC screen if it appears.

4.  Type powercfg /hibernate on and press Enter. You can then type Exit and press Enter to exit out of the command screen.