Plato said:
Every MS OS is best installed totally fresh. Always has been, perhaps
always will be.
I don't at all agree. Unlike with previous versions of Windows, an upgrade
to XP replaces almost everything, and usually works very well.
My recommendation is to at least try the upgrade, since it's much easier
than a clean installation. You can always change your mind and reinstall
cleanly if problems develop.
Particularly in this case--XP Home to Professional--this is the easiest anmd
most likely successful of all possible upgrades, since so little has to
change. Problems with it are xetremely rare.
However, don't assume that doing an upgrade relieves you of the need to
backup your data, etc. before beginning. Before starting to upgrade, it's
always prudent to recognize that things like a sudden power loss can occur
in the middle of it and cause the loss of everything. For that reason you
should make sure you have backups and anything else you need to reinstall if
the worst happens.