Oh my goodness! Those Compaqs usually come with a Microsoft sticker wheich you need to attach to your system case. The CD key code is printed on the sticker, and if you've used the Recovery Cd (which it sounds very much like you have) without finding the CD key code first then you might just be up the proverbial creek!
Unless you can find that sticker of course. Is it stuck to the PC somewhere, or still there amongst some junk?
If Windows 98 is installed and running, then you can retrieve the CD key from the Registry, as I indicated in your other topic. But if the recovery CD has been run, and you haven't got the CD key then it's too late, I'm afraid. You have two options:
Contact HP (who took over Compaq) with the serial number of that PC and see if they can locate the CD key code for you in their records . (doubtful)
Purchase another copy of Windows so you can format and install it, and download any necessary device drivers from the HP website.