Help needed with 6 month old pc build

Hey my fist post, so sorry for the noobiness.

My PC spec as follows.
MB p8z68-v lx
CPU: intel i5 2500k CPU fan and heatsink coolermaster
GPU: gtx 560 asus 1gb
RAM: hyperx 2x 4gb
PSU: gx bronze 750w

I have a custom built pc which is 6 months old. On a couple of occasions during first booting the pcu fan error came up, and after formating the OS, the message stopped.
Anyway i opened the case to connect the front end audio ports to the MB today and upon turning the tower on again, i was met with a blank monitor and no audible boot “beep”.
After resetting the cmos, it went to boot screen, and then the cpu fan error message came up. The fan is on and the cpu temp is 24ish, but it didnt sound perfect. Idisconnected the fan from the heatsink and cleaned. Again when i turned on the tower it didnt boot. Is this a MB issue? Id like to solve the issue myself but could anyone troubleshoot any ideas? It was my first build, so im still learning:confused:

Hard to say, but the boot failure sounds a bit like a PSU issue. Does the MB have an LED status indicator?

It went to boot screen again, but the speaker port doesn’t work. Anyway, I disabled the lower fan speed check in the bios, and the error message has stopped. I thought it may be a PSU issue, because of how the fan was reacting, but now i don’t know. there are two LED indicators that i know of. One is a memory check and one is for MB power. They are both indicating that things are fine. In any case the system seems stable at the moment…

it is a bios inssue before u update the bios you shoul´d put the current bios to default settings. then boot and download the latest bios from your Motherborad manufacturer and put the file on a usb stick in the root directory easier for you to find.
go to the bios setup screen and flash the mobo with the updated bios.
Now put you´re finger in the power button and press it until the PC shutsdown.
put the Power once again in the power button and go to the bios screen and load the default settings and save —>exit.
youre pc will reboot.
let it boot to the OS.

The only way to Build Computers is to start from square one, Case, PSU, MB, Memory, and Graphics. Fire it up and see if all those things work properly, if not find the problems and fix them before going any further. Go back to this basic set-up and see if you still get the CPU Fan error, if you do the Heat Sink and Fan are not set-up correct. :cool:

I noticed you stated you have a CoolerMaster CPU cooler.
If it happens to be the Hyper 212 EVO series then I came across this myself with an Asus motherboard.

The CoolerMaster EVO runs very slow when the CPU is cold, and the warning setting in the BIOS is set for 600RPM.
Reduce the BIOS setting to 200RPM, and the all will be well.