|He hasn't said what he tried to install XP from.|
He could be attempting to install it from a properly prepared bootable USB flash drive that has files from the XP CD on it, or from Recovery disks for the model, or ?
If it has no built in optical dreive, in most if not all cases, you CANNOT install XP from an XP CD in an external optical drive because the initial files loaded from the CD CANNOT recognize the PnP ID string of the USB optical drive you're using.
In that case, the CD is recognized as bootable, you can boot the computer from it, but all you see is s a blue screen and nothing further happens.
If that applied to his case, he would NOT have seen this...
"Now when I try to reinstall Win XP it tells me there is no hard drive."