I'm afraid the previous answer is correct, in that this model Compaq already has USB ports.
http://h18000.www1.hp.com/products/quickspecs/11456_na/11456_na.HTML
See? There in the diagram of the back of the unit, are two USB ports.
Now, the ports YOU were asking about, the ones on the *left* hand side of the laptop next to the disk drive, are called PCMCIA slots, or PC card slots. You would purchase a PCMCIA USB card... demonstrated by this Google search here for that exact term...
http://www.google.com/search?q=PCMCIA+USB+card&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
No, I'm not telling you where to buy them... I'm just showing you how a search for that phrase turns up multiple retailers... thus if you were to go to a store where they sell computer hardware and you were to ask for a PCMCIA USB card, that is what they would turn up for you. That is the card that slides into the computer, and provides 2 to 4 USB slots.
http://shop.ebay.com/i.html?_nkw=PCMCIA+USB+card&_armrs=1&_from=&_ipg=
There is an Ebay search for it.
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