Just a thought I haven't seem really discussed much. Do you have a different case/PS for this? If not, your budget of $80 just went in the toilet. As
videobruce mentioned, you may not be able to use the old Compaq case/PS. The older Compaq's had quite an assortment of proprietary components but I am not sure about the case/PS so you'd better check it out.
Even if you do have a case (or can use the Compaq one), your budget of $80 might still be a sticking point. Just doing a quick check on NewEgg, I couldn't get under $100 for both a MB and CPU. Those were a KT133A board and Duron 800 CPU. Came to $105. Maybe you can find better deals on PriceWatch.com, but you also have to sometimes deal with "shakey" retailers. I did a quick check there and yes, you can find some for ~$75+, but again, you will "takes your chances."
One option might be to "hang out" on the FS/FT Forum here on AT. Sometimes good combos can come up. Another option that I could not get the Pricewatch site to search for is the PC Chips M810L v7.1C based board/processor combo's. It is a MB with a "built on" Duron CPU. If I remember correctly, these are pretty inexpensive. Considering the planned usage for this system, that might be the way to go.
You can check out the specs for it on the
PC Chips site. Just click on Socket A ant then the first one in the list is that board.
EDIT:Upon further review, I'm thinking that board is a mATX form factor; not ATX. It "says" ATX on the site but it sure looks like the other. In fact the dimensions are that of a mATX. So, if that is not what you want, ignore the suggestion.