Windows Password Issue – Laptop Asking for Password Without Hard Drive

One day my laptop got infected by a virus, and I cleaned all those suspected infected files with Avast! Antivirus. I didn't check what kind of files are cleaned, since there are hundreds of it.

Now I realize it is a bad decision. After that, Avast asked me to restart – which I did – and when I boot again, my laptop asked for a password that I never set in my lifetime. It looks like something like this:

I tried guessing the password many times but it always fails. I'm afraid that this means two things:

1. Avast accidentally deleted the Windows system file, so somehow making Windows asking for a password
2. The virus from earlier sets the password (though this kind of thing didn't occured before Avast cleaned the suspected infected files)

Then I thought, "if I remove the hard disk, I could access it just fine since the password is set in Windows." So I tried to remove the hard disk and turn on the laptop again.

But I was proven wrong!

This is what appears on the screen as soon as the computer is turned on:

Now I really do not know what to do. I suspect that this is a BIOS password, but I'm not sure at all.

So my question is:

1. What happened to my laptop, and why?
2. Is there any solution to bypass or reset the password, so I could access it normally again?

My laptop is a Toshiba Satellite M300.