The old disks are most likely for an earlier Pavillion. To that end, the included drivers etc will not be compatable with the the new PC and its components. Also, the OS is probably an OEM version which means the license is only good for the original motherboard.
Traildriver is absolutely correct. Even if you could (though not legally) the new machine, I'm guessing, is running a 64 bit version of Windows and probably has more than 4GB of RAM. The Windows XP version on the recovery disks is probably a 32 bit version which will not recognize (utilize) more than 4GB of RAM. If you decided to go with a 64 bit version of XP you would need the 64 bit drivers.
I think Traildriver's response is the best answer.