Windows 7 - Suddenly passwords don't work. More complex than just chkdsk.

Client brings in a HP 27 omni all-in-one running Windows 7 home premium 64 bit.  
Suddenly yesterday morning they wake up and their passwords don't work.  
One standard id and one administrator.
Client brings over computer.  
I assume it's just a file corruption problem.  
I try to use a Dell Windows 7 64 bit disk to do a repair and run chkdsk.
But HP doesn't accept generic Win7 disks.
I use NT Password breaker to wipe out the password on the administrative id.
(This is lucky because if there is file/folder corruption NP password breaker might not work.)
I log on the administrative id and do a chkdsk /f from cmd prompt.
It runs the next time I reboot and now I'm able to use the password to get into the non-administrative id.
This confirms problem with file/folder corruption fixed by chkdsk.
Client comes over.   We reset password on administrative id to original.
She takes computer home, plugs it in and is locked out of her userids again.  She calls and I tell her I'll go over to her place tomorrow and fight with the problem.
I have no immediate explanation other than virus/malware.  I'm afraid I'll get into some endless struggle that will take me forever to figure out and for which I can't possibly bill for time I put in.  I have more than enough on my plate right now.
Do you have any rational explanation for this?  Or way I should go about debugging the problem.
Alan SilvermanOwnerAsked:
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NinjaStyle82Systems AdministratorCommented:
I would suggest backing up data and reinstalling Windows. It probably isn't worth your time to continue fighting it.
JohnBusiness Consultant (Owner)Commented:
You reset the passwords and the regular and admin accounts work. You said that above.

She takes it home and the passwords don't work. I don't understand. All she did was turn it on and the passwords do not work.

Windows runs as a service before logging on, so she would appear to have a virus outbreak in her home system, or a virus problem on the problem computer that causes problems on start up.  Look for a root kit virus with TDS Killer (Kaspersky).

Is it faster to back up and reinstall Windows?  It likely is in this case.
MASEE Solution Guide - Technical Dept HeadCommented:
Did you try resting password.
If not please check this
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Test the disk using the HD manufacturer's diagnostic tool, and if it finds errors it can't repair, replace the disk with a new one. You will have to use the recovery DVD's the user made when he first got the PC to restore the system to factory defaults if that is the case. If they didn't create those DVD's, check whether you can still do that using HP's utility they installed for that. This of course will only work if the recovery partition is still in good enough shape. Otherwise you'll have to order a set of recovery DVD's from HP.

You'll find the diagnostic tools of the different disk manufacturers on the UBCD:

Also run a memtest86+ to test the RAM. This is also included on the UBCD.
David SankovskySenior SysAdminCommented:
If there's a virus breakout at the client's network, reinstalling the operating system could be a very temporary solution, as the computer will be reinfected!
Aren't other computers in the network affected as well?
did you check simpler things like a faulty keyboard?

or usb stick or (boot) dvd? or a faulty disk because of loose connections.

is it old bios or uefi?


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JohnBusiness Consultant (Owner)Commented:
Alan - please let us know about the possible coincidence of hardware issues as suggested as causes of the passwords getting changed.
Alan SilvermanOwnerAuthor Commented:
All good ideas.  When I go over I'll try what you suggest.  First look for rootkits and viruses.  But then  I'm wondering if a upgrade reinstall of Win7 might be the way to go.  That would take the least of my time so long as I don't have to sit there and watch it while it updates.

What would you tell the client something like this might cost?  I charge $75 an hour and $100 an hour for emergencies.  She gave me $100 for yesterday's work. (It was a Sunday and I took it immediately.) But this thing, as it looks now, could take hours.
There's no point upgrading the OS or scanning for and removing malware from a disk that is bad. So you should first verify that.

The Price you charge generally depends on where you live and how you are organized. For example if you have to go to the customer you would charge for the way and the hours you are at the place. If you can do it in your shop, then you can do other things most of the time while the PC is working or the OS installing. So then you can charge less than an hourly rate. In the end it depends on what you will have to do. It also depends on whether you have to order recovery media and buy a new disk, that you'd have to charge separate.
Alan SilvermanOwnerAuthor Commented:
sarabande got it.  it was the keyboard.  HP wireless keyboard.  Plugged in a wired keyboard I had and the passwords worked. Am I glad it was that keyboard.  Simple is good.
Thanks to all,
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Windows 7

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