Maybe...maybe not.
I've changed CPU's on some systems and had XP fire right back up ...recognise the new hardware and continue on with no hiccups.
But it can go the other way as well and refuse to boot properly.
If this happens the solution is a
Repair Install of XP...
I suggest reading it thru to get familiar with the steps outlined and printing out a copy for reference.
If done properly you should be good to go...
You may have to re-register XP ...i use the 800# myself for this.
Good Luck.