I have recently loaded Win 7 RC Build 7100 on my Acer TravelMate 4000 laptop and the power (battery) icon is greyed out in the 'Turn System Icon On or Off' pane, preventing me from turning it on.
It seems to be a very common issue with Win 7 judging from some of the forums I have been going through.
I have tried enabling (by disabling "Remove the battery meter") through the Local Group Policy Editor, but to no avail.
I also have Win XP SP3 on the same laptop on a different partition and everything works well.
It is really annoying not to be able to see how much battery life is left and I would be ecstatic if someone knows of a solution. Cheers