Dell XP reinstallation disk will not work in your HP because it must be detected by the EEPROM to verify that it is a valid Dell (not HP) install disk.
Contact HP to see if they have any install disks remaining for that model. If they do, they will charge you $27 but that includes priority FedEx or UPS shipping.
If your hard drive has not bee previously replaced, then it has likely gone South and requires a hard drive replacement. Get the correct install disk from HP, then download all the drivers from the HP website, and you will be back in business.
Then you can recover most of your data installing this old drive as the <Slave> or using an external USB enclosure to copy the old data and emails.