I do not know the history of this machine except the client called me when it would not bootup. My assessment was that it would boot, but could not find the HD. I put an old drive into this machine, and it booted OK. Original HD was not recognized in another computer so it appeared to have failed totally. Dell supplied me a replacement 80 GB drive for the old 20GB. The jumper is cable select, and at bootup the drive is recognized. I then used the Restore CD (newly supplied from Dell) to install Win XP with SP 2. Now at bootup there is this PandP error message. I have replaced the MB battery - but get a message battery voltage is low! RAM seems to be recognized, but I noticed it is not original - and the two modules are from different suppliers. Other than the HD I have not replaced any hardware. BIOS shows IRQ5 reserved; all others, available. After pressing F1 to continue, Win seems to be installing. Might mismatched RAM be the source of this problem? What else do I look for?