My pc powers up but never starts the monitor or run through a full boot up. all fans operate. changed monitor, same error. any ideas?

that means just what it tells you
the PC is dead, PC video dead or video cable unplugged , dog chewed it , pins bent or plugged in wrong on 1 or both ends.
or monitor not selected to the correct input port (OSD)

PC power lamp glowing not amber or blinkikng
PC fans spin , PSU fan and CPU both
if PC has GPU card in PCI-express slot it must be use those ports only for video.
PC not beeping
PC not texting errors post.
PC not blinking codes on LED or caps lock or POST ERRORS !
NO PC told
PC dead.
PC not stuck in sleep mode , hold PC power button for 10 full seconds to end it, (cold boot that is)

test monitor on end good PC? yet?

what fan there are 3!
ok, first things first.
an old desktop.
HP Pavilion Elite m9515y no monitor stated,
did you fist test the monitor to be sure its OK, on any other PC
simple tests, like this help, for sure both bad......!
did you know a 2002 monitor has and internal sleep timer clock that can be very confusing, no monitor stated make or model.

at least.
it is dead pc for sure. fan dead = dead PC.

let me say it sounds to me like the PSU is dead.
right off.
but I do tests first.
is the fan on the CPU running full RPM with power on?
if not pOWER IS NO GOOD, or the fan is no good
the fan must spin or the PSU is bad
OR !
or the PSU found shorted parts up stream.(power bus)
all PSU can shut off in 1second less.,
we strip the system down to make sure there are no shorted
devices there.

unplug , all HDD, SSD and DVD/ CD drives
all PCI cards out
does the power stay one now, and CPU fan turns. fast
or is it all packed up in lent. as all do.

PSU dead , 1,2,3'4,5,6.... (we use voltmeter)
http://www.pcdied.com/power.html#tool-less



ever clean the best out? every year.
as seen here,

http://www.pcdied.com/overheated.html


that PC will overheat. easy
fans stall.
vents blocked
all that. bad bad bad.to the bone.
the CPU will shut down overheated, all due
(intel inside or AMD) both do . self preservation mode.

Open it again and make sure you connect all the devices and such ..It seam to be like a clear case of a disconnected cable ..If the system boot up ..and seam to run ..try to see if the vga secondary monitor brings anything to a screen ..if it does it means you messed up with the monitor connections ..cause you changed the hard disk ..you don't have a operation system to boot into and try to make an idea..but its a start ..
Other things to check is the fan connections and cables ..
If the screen is totally blank I think is like I said just a bad connection to the monitor or a damaged cable in the process of opening it .In any other case you would have at least a warning on screen even without hard disk it should boot to BIOS ..

IF you are sure its not a problem with the monitor--and from what you say it IS getting some power and if you are not getting any beeps--Can you boot to the BIOS? If not ,could be a problem with the power supply-check output voltage and/or test with known good one (cheap on Ebay).
By-The-Way- It can be a good anchor, but only off the stern, just to keep the boat from swinging

Before anything else, open your case and make sure all power and data cables going to motherboard, disk drives, etc are firmly seated, and remove and re-install memory sticks in the same locations. Sometimes temperature changes inside the PC can cause these connections to loosen. If that doesn't fix it, do you hear the noise of the cooling fans coming on? If you do, check your monitor for a green light. If you get a green light on the monitor and fans are powered up and running and you get nothing else it could be a hard drive issue. Try booting from CD in that case. If fans come on briefly and then shut off, or fans stay on and you have no green monitor light, this could indicate an issue with your processor or motherboard.

With the little bit of information presented, it appears that this is possible a power supply problem. One thing you can try is to unplug the power adapter from the laptop, remove the battery, then plug the power adapter back into the laptop. Then try to turn it on. If everything comes up normally, then the problem points, potentially, to the battery.
Hope this helps!

Possibly overheating? As you say that when you press and of the F-Key option nothing is happening, and also the fan is running at full power, if the fan is louder than usual, then it could be overheating in the air vents which you can find either at the sides, back, front and underneath the laptop, try getting the compressed air, and giving the air vents a blast to get all dust out. Or a vacuum. Do it whilst laptop is turned off though!

It seems that you don't have any Operating System installed. You need some bootable OS setup disk, and change BIOS settings to boot you PC from CD. Insert disk and restart PC, then follow onscreen instructions to setup OS.

I would start with a new power box, then a motherboard. then the hard drive.

booting files corrupted try to boot by inserting windows 98 bootable cd or windows xp bootable cd