I suppose that depends on whether...you value a trashed system...or you prefer a system with a chance to run properly.
BTW: If this cousin is giving you a system...make sure that he also gives you the drivers CD and XP CD and the XP license data that should come with it.
Or be prepared to legally acquire the version of XP that you intend to install (approximate price, $90).
You might also inquire...why you are the recipient of all this goodness...if the system is worth fooling with
. In other words, what don't you know now...that you will wish you had known...within 30 days?
That's the way that I would approach things.