If i were you i would pay the 20 dollars shipping and get them. Eventually they will stop carrying them, and also its better then pay 200 dollars for windows xp cds from microsoft. I usually store all my cds in a safe place, just in case i need them.
Or may I recommend... Give windoz the boot and go with Linux for free. I know, I know... but I love it so.
Ok ok, so here is the deal. Its a compaq computer, that needs windows reinstalled. I have the oem cd from dell. When you try to reinstall the oem cd on a dell it asks you for the windows key. The Key for the dell is on the outside of the cpu (or box). Its the sticker that says windows certified product etc... The question is the compaq has the same sticker with a key on it (different numbers of course). I'm wondering if that when the CD asks me for the Key can i put the compaq windows sticker into the dell windows CD??? The out side of the CD has dell written all over it. But on the inside I could find no reference to the manufacture.
I don't think it will work. The Compaq almost certainly had "its own OEM version" originally installed. All you can do is spend the time and try.