According to HP, you should be able to run 16GB. Where did you get the RAM you installed? Are all 4 DIMMs matched or do you have 2 pairs of different models of RAM? What make/model of RAM did you install?
There are times when populating all 4 DIMMs (especially with 4GB DIMMs) that power issues can occur. That may not be the issue here and your OEM BIOS is not likely to let you tinker with the settings very much.
Your system specs can be found here:
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c02016581&tmp_task=prodinfoCategory&cc=us&dlc=en&lc=en&product=4160015#N271
Your available downloads can be found here:
http://h10025.www1.hp.com/ewfrf/wc/softwareCategory?cc=us&dlc=en&docname=c02016581&lc=en&product=4160015&