ok go into the BIOS it normally says how to at startup by pressing delete or another key. Then look for something daying health monitor etc look for CPU temps make sure there not high say 60C+.
ok now about the error use your bros comp and follow that guide how to put the floppys onto cd.
It should go through part of an xp install im not 100% sure iv never used the floppy disc method...
anyway the first screen should say press r to repair if you press r it`ll go into a black screen that is the wrong one.
What you do is press enter until it gets to a screen showing you what version of windows you have then you press r on that screen it should have the option.
here is a link showing you what you should see or something similar:
How to: Repair Windows XP/2000 if you are unable to boot into Windows. - TechSpot OpenBoards
the 3rd slide is what your looking for and it should look like its running through an xp install cant remember if it asks you for a serial again or not though.