|Someone must have installed Windows from scratch without installing the drivers the system needs.|
Whenever you load Windows from a regular Windows CD (or DVD) from scratch, after Setup is finished you must load the drivers for the mboard, particularly the main chipset drivers, in order for Windows to have the proper drivers for and information about your mboard hardware, including it's AGP or PCI-E, ACPI, USB 2.0 if it has it, and hard drive controller support. If you have a generic system and have the CD that came with the mboard, all the necessary drivers are on it. If you load drivers from the web, brand name system builders and mboard makers often DO NOT have the main chipset drivers listed in the downloads for your model - in that case you must go to the maker of the main chipset's web site, get the drivers, and load them.
Your Dell model may have come with an XP Home SP2 re-installation CD - it's a slightly modified regular OEM XP CD, and can be used the same way asone on your model. It may have also have come with (a) CD(s) or (a) DVD(s) that has the drivers you need to install on it, and possibly programs (applications) that were included in the original software that was originally on the computer that you can optionally install. If you're the orginal owner of the computer, you should have those somewhere; if you bought it used - maybe not.
If you have the latter disks, install the drivers and programs from that. Install the main chipset drivers first.
If you don't have that/those disks...
Go to the Dell web site and find the specific drivers for your specific model, download them and install them.
You will need to install or get at least the Ethernet drivers, on another computer if you need to (e.g. copy them to a flash drive) , in order to be able to access the internet, if you're not already connected to the internet wirelessly. If you're using a wireless or wired network adapter than didn't come with the computer and plugs into the computer, you'll have to get the drivers for that from the maker's web site, and even then that may not work correctly until AFTER you have loaded the main chipset drivers
If Chipset drivers are listed there, install those first.
If Chipset drivers are NOT listed there, go to the maker of the main chipset's web site, get the drivers, and load them first.
That's usually the Intel web site for Dell computers - get the notebook or laptop or mobile chipset drivers.