The board in your link actually describes itself as an ATX. The third photograph from the left shows the position of some of the holes but not very clearly. Before spending £195, I think it best to remove the board from the HP case to see the hole configuration on that. I also have concerns about the PSU in the HP case - many of theirs were one-offs but as I said before, cases are cheap and you could find something quite flashy on e-Bay for under twenty quid. Good luck with the build.