Did you ever get the problem solved? I have the same problem (XP Home to XP Pro upgrade), have downloaded and installed all updated drivers in the order recommended by Dell and hibernate/standby options are not available anymore. It also seems like the sensor that used to detect a closed screen (used to have the system hibernate) does nothing.
I downloaded the Quickset, selected enable hibernation, but the settings never remain in effect.
Any help would be greatly appreciated, or if anyone else out there has had a similar issue and found a solution to it, please let me know!