XP error loading

I have recently encountered a problem with XP Pro.
when the system starts to load I get a choice of

1. Windows XP professional
2. Windows(default)

When I choose 1, I get an error that "root\system32
\hal.dll is missing. Reinstall this file"

after pressing any key I restart and come back to the same
screen. If I choose 2 windows XP loads and works fine,
mostly. But the second option it runs everything as if it
is the first time it has been run, i.e. NO files imported
to media player, Warning screens etc. All my settings are
the same though. How do I replace a file in my "original"
windows.