Hibernate is a feature seen in many operating systems where the contents of RAM is written to non-volatile storage, such as the hard disk (as either a file or on a separate partition) before powering off the system. Later the system can be restored to the state it was in when hibernation was invoked, so that programs can continue executing as if nothing happened. Hibernating and restoring from hibernate is also generally faster than a hard reboot and, if necessary, can be done without user interaction (unlike shutting down, which often requires the user to specify if open documents should be saved).

To use hibernation the hard disk needs to have at least as much free space as there is RAM on the system.

Hibernation is often used on laptops and can generally be set to happen automatically on a low battery alarm. Early implementations of hibernation did use the BIOS but on modern systems the functionality is usually handled by the operating system. Hibernation is defined as sleeping mode S4 in the ACPI specification. Ref: http://en.wikipedia.org/wiki/Hibernate_(OS_feature).

Microsoft introduce hibernation in Windows 2000 and later. To enable hibernation, your Windows reserves a hidden system file (usually at: c:\hiberfil.sys), the file size usually equal to the total amount of RAM on your system. If you have 4GB RAM, the hiberfil.sys file size will also equal to 4GB.

If you are on a desktop/workstation or a system that always on, you don’t need Hibernate feature.

There a few way to disable Hibernate in Windows Vista:

Using Windows Vista Disk Cleanup:
[*] Click Start >> All Programs >> Accessories >> System Tools >> Disk Cleanup
[*] Select the drive where Windows Vista installed.
[*] Wait a few moments while Disk Clean up calculating space.
[*] Uncheck all except “Hibernation File Clearer” and click OK.
[*] Done, verify the hiberfil.sys file is not exists.

Using Windows Vista command line #1:
[*] Press: Windows Key + R
[*] Type: cmd (without the quotes) and press Enter., it will open a command line window
[*] Type: powercfg -h off (without the quotes) and press Enter.
[*] Done, verify the hiberfil.sys file is not exists.

Using Windows Vista command line #2:
[*] Click Start
[*] Type: powercfg -h off (without the quotes) in the “Start Search” box and press Enter.
[*] Done, verify the hiberfil.sys file is not exists.

Good luck!