Sign in menu choice greyed out

Thanks. I did all of the above just now, and no change.

Any other thoughts?

Thanks!

Hi -- is anyone out there? Please help!

Thanks!

Hi,

More info:

I think several months ago I was playing with Terminal commands, turning on and off the search index for some arcane reason (some software I was working with required me to do so -- using sudo commands I think -- I could look up my notes if need be) -- and something went wacky.

Now I'm trying to upgrade to El Capitan, but it gives me an error saying I can't download from the account I'm logged into -- try logging into a different account. (This could be because the computer was a gift from a family member who works IT at a big company -- they cycle thru lots of computers -- so the account is probably the IT guys account).

Hence the reason I'm trying to log into a different account.

Does this make any sense? Am I totally messed up?

One last question -- is there a way to download a fresh copy of the App Store thru a channel other than using the App Store?

And if so, how does one un-install the current App Store?

Thanks!

Close but not quite. Refers to logins regarding apps; not the entire sign in process itself.

Any other ideas much appreciated...