Unfortunately no, the XP license on the HP machine is not transferable. Windows licenses that come with pre-built PC's from manufacturers like HP and Dell use a Microsoft Windows OEM license that states the license is associated with the motherboard and is not transferable. So you would not be able to legally use the HP XP license to use on or use as a basis to pgrade the new machine. If the old XP machine used a different, Retail Windows XP license (for example from a separately purchased copy of windows from a store) that would be tranasferrable. Sorry.