Tomex

First off this is my first time messing with the inside of the comp so please bear with me.
Somebody recently gave me a HP pavilion xt878,
I know its old but its better than what I have now,
at first it wouldn't even start up.
Took off the case cleaned it up and got it to turn on.
First time it booted up into windows me and froze so I shut it down and tried again
this time it did not make it to windows
instead it said operating system not found.
Shut down again checked all the connection tried again
it went into windows looked like it was frozen again
then it flashed to a blue screen and said something to the extent of cannot write to drive C
gave me two choices of keys to hit
but the keyboard or mouse would not work.
Someone told me I should take the HD out hook it up to my comp
format it and completely erase everything and go from there.
Hooked it up to mine
when you boot up it says boot disk not found press F1 to try again
or F2 to go to settings
well once again the keyboard does nothing.
The keyboard is a USB connection so is the mouse.
The comp I have now was built by someone a long time ago
has a Pentium II old as dirt,
power supply has a couple of connections that go to nothing
that have P3, P6, and P9 written on them.
I hooked up the HD from the xt878 to the P3 that comes out of my HD drive in the Pentium II.
Guess what I'm asking is can I
hook up this HD drive and format it?
Is that what I need to do to get the xt878 to work?
The HD is a Maxtor model# 98196H8 hope this makes some sense.