XP allows you to span drives (behaves as one).
But...
You best have good backups, because a single drive failure can hurt big time as some parts may be on the
other drive.
Why not clone the old drive to a NEW, bigger (1 or 2T) drive?
Most drive kits come with the software that allows resizing while cloning.
I think I saw a 3T drive for under $100US

(My first 40M drive cost $400)