The Hibernate option is not available in Windows Vista

Cause:
The Disk Cleanup Utility and has been used to delete the Hibernation File Cleaner,hibernation feature is disabled.
Symptoms:
Solution:
use the PowerCfg command-line tool to enable the hibernation feature
Details:
To resolve this issue, use the PowerCfg command-line tool to enable the hibernation feature. To do this, follow these steps.
1. Click Start, type command in the Start Search box, right-click Command Prompt in the Programs list, and then click Run as administrator If you are prompted for an administrator password or confirmation, type your password or click Continue.
2. At the command prompt, type powercfg /hibernate on.