It is a very easy task enabling hibernate in windows xp, but it's different approach to do in windows 7.
If you want to see the new Hibernate entry in the Start menu, try it:
1.Type CMD in Start menu and then press Enter to open Command Prompt. Note that you should have the administrator rights.
2.type the command as below:
powercfg /hibernate on
and preess Enter
3. Type exit.