Sony keyboard and touchpad stopped working after Crash

1- I've had a Sony VAIO Z Series. I used to connect it to an external keyboard, mouse and monitor. A couple of months ago, it stopped working (it really has a looooooong story completely documented in until I realized the HDD was dead. After that, not only the HDD is dead, the keyboard and touchpad do not work either so I cannot get to BIOS with the keyboard (if I use my external keyboard that used to work with, it knows the keyboard and I'm fine ... the problem is that I wanted to sell the lappy but the guy was scared knowing the keyboard doesn't work so I decided to try to get it to work!!!!!). My question is that, how much do you think it's likely that if I put a working HDD into it and reinstall the windows, the keyboard and touchpad start working again?

Any hard drive will work fine as a replacement, providing it is the correct type (SATA/IDE). Try and get one that isn't too large as the main boards often support up to a particular size. If the drive is larger than the compatible size you will either not be able to detect the drive at all, or you wont be able to use all of the drive's capacity.

It is also unlikely that if the keyboard does not work within the bios, that it will work within an OS. This is because the hardware is detected by the BIOS and then handed over to the OS - if the keyboard doesn't work on toshiba satellite p875 keyboard a hardware level, it wont work on a software level. (Note: this is not always the case however).

If it were me, I would pull the laptop apart and check the cables for the keyboard and such are still connected etc if they are; I would install an OS and see if this will work. Failing that, flashing the bios is the next item of agenda but it does seem that the laptop is no longer of serviceable value.