Almost any modern distribution would do. Make sure you know how to burn an iso before going. Burn a knoppix CD if you want to test linux first, which you should. Modern distributions like SuSE, RH and Ubuntu should all have the HP laptop support built into the kernel. I recommend suse, but only because it automatically will resize your harddrives and such if required, but it also installs into blank space. But all distribs have there advantages... Hell, ubuntu probably has a better installer (But i am out of blank cds. Want to try it, but i cant until i find some cds..) Make a good choice. And hey, if you ever buy a new desktop, you could expeirence some cool eye candy with even more modern Oses(Beta suse and some versions of ubuntu now support Xgl, which is a 3D Xserver. I dont know of any other distribs that do this.)
Just make sure everything works. If youve ever installed windows before, you have had to deal with drivers etc. If something doesnt load in linux and your computer is properly configured, you probably need a hardware upgrade, because the linux kernel is quite good at hardware support. But then again, you probably already know this.