Hi Welcome to JustAnswer.com I am Tech Specialist and today, I will be trying my best to solve your issue.
Do you see this when you start the computer?
Please restart the computer and when it reboots, keep tapping the F8 button
Advanced Options Menu should appear
in that menu, choose normal mode or last known config and press enter
Strange, can you check if there is any usb device attached to the machine or any disks on the cdrom
ok restart the computer with F8
choose safe mode this time and see if you can login
no problem, I am waiting
Exactly what is the message?
Did it went to the desktop or stuck in c prompt?
Reboot the computer and tap F8 again at reboot
Let me know if you can see a repair your computer option there
ok please let me know if repair my computer is present
:( Try using blank password
Great, what are the options?
Yes but do not use anything without my suggestion.
use that one, system repair - system restore and restore the computer to a date when everything was working fine
NEVER use factory restore coz you may lose all data if you use that
use the simple system restore
I think you are infected with some Malware which caused this
can you try it again, choose a much earlier date to restore
You must have selected startup repair
choose system restore
go to repair my computer option
Ok which date did you restore to?
Please HitmanPro from the following link and save it to your desktop: http://www.bleepingcomputer.com/download/hitmanpro/
Use this computer
from the one you are talking to me
We need another computer to trouble shoot this else we are stuck
In that case, we are stuck here.
Can you arrange one or may use your neighbor's computer?
If you are okay with restoring it to factory, you can try that but in that you will lose all data
Do you have lot of data on the computer?
In that case we need another computer using which we can create a kickstart usb drive to scan the computer
One thing we can try
One of my fellow experts and friend suggested this
in the command prompt, can you type this and press enter
ok choose a date now
much earlier when system was all working fine
I will give you a software to do that
ok, let me know when done
how is it going on?
Yes, just download and install malwarebytes free version: http://tinyurl.com/d5jtuzRun a full system scan using it.
That should do it, let me know if any further questions or kindly rate me below
most probably it needs a clean up