Issues after the PC crashed

My mom was using the family PC which has 3 accounts on it (Windows 7): One for my sister, dad, and mom. While my mom was streaming youtube videos, the computer crashed on her although she can't remember what it stated. So after the computer reset, she noticed the time had changed but she wasn't able to change it. The user account control screen popped up which showed my dads account and sisters account and it requested her to put in a password for either of them. Keep in mind, neither of those accounts had passwords setup. So I went on and started to look into it. At first, I tried to get on the net and I kept seeing the message appear that the site wasn't trusted. Sites like youtube, google, etc. I logged onto my sisters account and was able to change the time to the correct time, which allowed me to use the net on my mom's account. The problem with the "user account control" popping up hasn't gone away though. Anytime I need admins rights to use a program or whatever, that UAC screen pops up asking for the passwords, which again were never set to begin with. When I try to enter my dads account, it states his password has expired and that a new one needs to be set, so it asks for the old password so that I can set the new password... Not really sure what's going on here.

I tried checking the disk for errors
I scanned the computer with the AVG, malwarebytes, and spybot thinking there was some kind of virus
I tried restoring the system back to a week ago

Everything checked out ok and the system restore didn't change anything. What else is there to look for?

Hi

Also go to Start --> Windows update, to check for any security and critical updates available.

Date and Time is one common reason for such thing to happen.
When i want to update/install Android apps, it prevent me from doing anything.
It was then i note that the date/time went back to ancient time.
After reset date/time, it is back to normal.

One more point on the Date/Time.
How old is the computer.

Maybe it is time to change the coin battery on the motherboard.
Date/time may be affect by this coin battery.

Not necessary to do now if it is done.
When next time this do happen again, go to BIOS to confirm on the date/time is faulty or not.
If faulty, then replace that coin battery.

The computer crashed for some reason and it can have corrupted files.

Schedule a disk check: Open CMD window and type chkdsk c: /f
Run a System File Check : Open CMD window and type sfc /scannow