PC won't turn on, there is a red light, and i've tried all sorts to work it out

My PC wont turn on, a red light comes on and i hear the fan spinning but that's it, nothing on the screen, cant hear the hard drive working or anything. At first i thought it was the PSU or CPU but i've tried a different hard drive, a different cpu, a different psu a different fan and heat sink, replacing the ram (there is no error beep either) and resetting the motherboard. I think it must be a motherboard issue but i'm not sure, can anyone help? The computer gave no prior hints that it was going to stop working, it blue screened a few times during football manager but that's all.

What kind of computer is it? If it is a self built, what system board is in it? You can try unplugging everything but power, video and ram. See if it will come up then start adding things back.

Hi, i actually can't remember any of that off the top of my head haha sorry, but it's a packard bell, and i've tried that and the thing that's causing the problems is the cable to links the psu and the motherboard and powers the cpu, so i dont know what that means. when its unplugges the pc dosnt switch itself off and the fan runs at full speed, is the cpu ruined? or should o reapply thermal paste? it's store bought

You may have a bad psu. Are you okay with swapping psus to test? If not, you may need to take this to a shop. Also, I havent worked on a packard Bell in some time. They may have an "In-House" type power supply - only used with their setups.

hi thanks for your help but as stated i already tried that im thinking its a motherboard issue due to the lack of beeps when i turned it on without ram...

If it is a motherboard. I think packard bells are proprietary - only their stuff works in there computers. I cannot be sure unless you give us a model. It should be found on the back or bottom of the computer. I know you said it was a Packard Bell, but there should be something to identify it. How old is it?