furthering yrag's instructions,
when re-seating the memory make sure that the memory contacts on the module are fully into the socket BEFORE latching down the memory module.
and from my googleing of the specs for rthe laptop,
I found a hp workshop manual (http://h10032.www1.hp.com/ctg/Manual/c02641795.pdf) that tells me that the craphics is INTEGRATED into the motherboard, and that there is at least two varients of the motherboard(one with an ati 4250 and onr without), and that there is two different amd 2.6 ghz cpus(AMD Turion II N550 and AMD Phenom II P650)and that the TOP processor is a 3ghz AMD Phenom II N660, and the 320 is a valid size of hdd for the machine (ranges from 160gb to 750gb
from the above info,
I would suggest check the memory is properly seated,
then try booting with an external screen and only powersupply(no battery) and ONE memory module at a time,
if neither screen displays with each memory module,
then it is most likely either a ram/motherboard issue or powersupply issue,
the cheapest test is to obtain a clone powersupply to suit the computer and test with it,
and if still faulty ten remove the hdd and BACK UP all the files and data on the hdd , then reinstall it and go to compaqs local service centre and sweettalk them.
hope this helps
harpo