from the sounds of how old it is, I would say it most likely would not fit. Motherboards have changed since the Presario. If I were you, I'd pitch in another $30 for a cheap computer case. Otherwise, you can always drill holes in your old case to make it fit. You can pretty much make any case fit any motherboard if you're determined.
You may use any micro atx motherboard if your backplate is removable. If you want to use your hp windows installation, then look for another hp motherboard. The power supply may have a 20 pin connector, buy my newer hp system came with this older connection on a 24 pin motherboard, leaving 4 pins open. It ran fine. Check ebay for newer boards; the Intel 865 chipset in socket 478 will allow you to upgrade your cpu and use your old ddr memory. I found a frys combo deal for $29.99 after rebate that would work with your case, but it's sold out almost everywhere.