If your XP Home Edition and XP pro disks have a product key and were never installed on any computer other then your Dell, your best option, in my opinion, is to carry on with the present installation. There is a high probability that a day will come that you will need to reinstall your operating system and then you will have the solution at hand. Please note:
1: XP, of any version, can be installed only on one computer.
2: OEM is cheaper then retail and is more limited in some options. Have a look here to learn more.
3: If both disks were never used then you can use one of them to install on another computer. Just don't mix the two. To avoid confusion I always write on the disk cover on which computer it was installed. Also, contrary to what is written on the cover I always keep the product key sticker attached to the cover (not to the computer). The reason is that I have seen more then one computer on which the sticker became unreadable.