Only the "CurrentControlSet" matters, but services are controlled by typing
services.msc into a Run... box
I think you need to set the service to Auto, then press Start. You also need
to set the UPS type (and for that you need the tab...)
As to what's happened to lose the tab, I'm not sure. There are registry
entries to remove the 'power control' applet completely, but none documented
that remove one tab. Any entry that did exist would likely be in one of four
places:
HKEY_CURRENT_USER\Control Panel\don't load
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
key, or possibly the equivalent HKEY_LOCAL_MACHINE key.
Since any entries in here only inhibit actions, it's safe enough to remove
any likely suspects and see what pops-up out of nowhere. If in doubt, export
the section to a .reg file first so you can restore it to how it was.
Since I'm not sure what the entry would look like I can't advise you on what
to look for, that would only be possible on a computer where the tab is
missing.
Some useful info:
http://www.virtualplastic.net/html/ui_panel.html