Are you sure the Compaq does not have wifi adapter inside it, every computer the last 10 years has had wifi, that would have to be one really old dinosaur of a laptop.
You must of heard wrong. Computers / motherboards don't come with Wi-fi these days unless you specificity buy a motherboard with one. What model is your PC, I'll have a look for you.
I use a power line adaptor. They work really well for me