The hp dc models have the intel security modual built into the mother board as well as the Intel Local Management Service (LMS) and Serial-over-LAN (SOL) support for Intel Active Management Technology (AMT).
This shows in the device manager as a "simple Pci device" or maybe a "serial comm device" with a yellow! that needs a driver.
Try this one, or search the HP site for "dc7800 simple pci device win7". Use the exact name from the device manager im your search.http://h20000.www2.hp.com/bizsupport/TechSupport/SoftwareDescription.jsp?lang=en&cc=us&prodTypeId=12454&prodSeriesId=3784892&prodNameId=3785037&swEnvOID=1093&swLang=13&mode=2&taskId=135&swItem=vc-65142-1