When i turn on my hp all in one computer,it's telling me cpu fan can not be detected

hello, HP motherboards are very picky on what types of fans you install.
question: your cpu fan, does it have a 3 or 4 pin connector?
do you get error msg when you first turn on your computer about cpu fan not present?

also most hp,dell,compaq motherboards have very limited bios features to monitor fans and other hardware,

Neither.

Turn the computer off.
If it is a HP laptop, remove the battery.
Disconnect the AC power.

Buy a can of compressed air, and give your computer a "blow-job",
to blow all the dust away from the heat-sink on top of the CPU,
and also, if it is a desktop, from inside the power-supply.

A layer of dust is a layer of insulation, preventing the heat-sink on top of the CPU from "radiating" the heat away from the CPU. So, your motherboard is detecting that your CPU is "too hot", and automatically speeds-up the cooling fan, to try to move the heat.

YOUR CPU FAN MIGHT BE VERY DIRTY OR IS NOT WORKING. YOU MAY CLEAN THE FAN AND HEAT SINK. AFTER CLEANING AND YOU TURN ON THE THE PC AND THE FAN DIDN'T WORK YOU CAN BUY THE CPU FAN TO A ELECTRONIC STORE SUCH AS FRY'S ELECTRONIC'S. HOPING THIS INFORMATION WILL HELP YOU SOLVE CPU FAN PROBLEM.

There are usually more than one place to plug in a CPU fan. Only one of them is actually for the CPU fan, and monitored by the system BIOS. Make sure your fan is plugged into the right connector.

It isn't detecting your fan as the fan may be dead or the sensor is dead. Both are not repairable but cheaply replaced and fixed with a new fan. The cost of the replacement cpu fan is not that much compared to a cpu. So don't try to make it last a bit longer by hitting the f1 to continue. That will catch up with you pretty quick.

If you want to double check you need to look at either the cmos setup section of a system monitoring software and check to see cpu fan speed and cpu temps. You may not see the speed but you should see the temps. If the temp is getting over 55-60 or more shut down and go get the fan. It's dead. If you see the rpms showing then you might have a motherboard problem.

However I would say you have a dead fan. Replacements are $5-15 and you need to just crack the case and pull the old one and put in the new one. You can take it to a tech but they will charge you to check it out again and then ti replace the fan and some shops will insist on new heat sink etc (those don't ever ever wear out or go bad at all)

One of the fan monitors in the BIOS is detecting a problem with a fan.
This would be a good time to pull the cover off the computer and clean ALL the fans. either a fan is dead or struggling. any fan in your computer can be replaced for less than 40 dollars.
Keep in mind that of the fan is weak and goes out, it may take the cpu or a video card with it.
Regards

tell me the wright way to remove 512 chassis fan error i am very depressed on this

the fan must be the correct fan
i guess you meant the CPU fan, ? desktops can have 2 or 3 fans.
the fan has 3 wires, in many cases, the 3rd wire is a RPM tachometer that if not correct the PC can not read RPM
if RPM reads 0 the PC will be very upset. and do that.
my guess you bought the wrong fan, and is super easy to do
giving the many fans
on some PCs the BIOS monitors the fan RPM and heat sink temperatures, or both, and tells yous fan bad for either failing

on my PC here, now, I can go in to bios and see both live sensors
RPM and Temperature. this allows for easier diagnosis
i dont think your PC has that page in BIOS to do monitors for trouble shooting, in fact mine has 3 fans all 3 are monitored, now.
high end PC .

this older desktop , only the m7200 pages are there. at hp.
so cant look at the fan nor BIOS.

i use a windows program that lets me watch the fan speeds
and all CPU and GPU core temperatures. (ask) its free.
the troubleshooting guide at HP stops short at this problem
says get it fixed. so you want to fix it your self sure.
so talk to one of the top, CPU/HEATSINK/FAN makers
and buy this from them.
if the fan spins fast and RPM is 0 wrong fant
if the fan spins fast and RPM is ok, then the BIOS dont like the CPU temperature... this has 3 causes.
fan dead. or slow. or wrong fan installed
heat sink fins packed in lint as all do ever year.
heat sink thermal bond compound failure, common.

Or did you connect the new fan to another 3 pin connector on the mainboard?