Well i have dual boot (Fedora 8 and Vista Business) and just yesterday i noticed that that vista seemed to lack hibernate option after searching in power options for some time i remembered about the command line config from earlier versions and luckily it still works. NOTE: IN VISTA ULTIMATE IT IS ENABLED BY DEFAULT

1)Open cmd in administrator mode

2) Type & Use powercfg.exe /hibernate on

or powercfg -H ON

Enjoy!!

NOTE :Hibernate in some systems makes it unstable on re-wakening