|In answer to what RAM to buy. Your HP probably doesn't have any options to adjust RAM voltage so you may want to buy RAM that is set to run at 1.8V. Some performance RAM may require a higher voltage and your board may not be able to supply it. |
If you want to you should be able to see if you have any way to control RAM voltage. If so, then the above is not applicable.
The RAM that jam linked to is an example of what I described. The specs on that RAM calls for 1.9V. OK if you can supply it.