ok, from what i see, it looks like the hard drive is directly under your touchpad, and that may be whats causing the heat issues. just out of curiosity, what speed hard drive do you have in your notebook? if its a 7200, this could be why you have heating issues. if you dont have a drive that fast, it could be due to a faulty hard drive that is overheating. it could also be due to your fan or the software controlling your fan and cooling sytems is failing. id recommend you get some software to monitor the temp and performance of your hard drive.
the one program id recommend for monitoring and benchmarking the hard drive is HDTune. its a great little peice of freeware. do a google for it and youll find it easily.
also, for future reference, if you wanna see what the insides of your notebook look like, and how its put together, check here.http://h10032.www1.hp.com/ctg/Manual/c00778754.pdf