try removing all cards but the video, and sec spu (if installed) all memory except for the first stick, now do a full cmos reset by power off, remove power cord , press pwr button 10 sec, then remove cmos battery, now press cmos reset 5 sec.
power on, confirm cmos reset (time will/date will be off)
power off replace cmos battery, power on set cmos settings do you still have the error?
if so pay to contact HP support, they might be able to help or motherboard replacement is required or try the items i listed below
https://support.hp.com/us-en/document/c04743732
http://h10032.www1.hp.com/ctg/Manual/c04205252
there is one other part that affects the fans running at max speed and that is the ambient temp sensor which is located in the power on cable/button. this cable has a small transistor embedded in the cable that which contains the power on button. if the transistor goes bad, the case/memory fans will ramp up to ful speed (cpu fans will remain fine)
offical solution is to replace the cable, which requires removal of the right side panel/left removable panel and front face plate. unoffical solution is to take existing cable, locate transistor, peal open covering and replace NPN2222a transistor
making sure you attach new transistor the same way as existing one
last solution is to use two 52 ohm 5 watt PWM (4 pin) fan speed reducers on the 2 front fans, and one each 52 ohm 5 watt resistors on rear case fan and the memory fans (the memory/rear fans will rquire you to cut the 12v line and insert the resistor)
the error msg will still be there, but the fans will run at close to proper speeds