I have Compaq CQ50 laptop. I had installed Win 8 OS on it. After 2 days of installation, the system started giving error "your pc ran into a problem and needs to restart" & restarting the machine frequently.
Hence I formatted Win 8 OS from C drive.
After this I am trying to install another OS such as Win XP or Win 7, but my laptop is not recognising HDD or CD-ROM so unable to install any OS.
I can provide more inputs if required to diagnose the problem.
Are these components not recognised by the laptop's BIOS ?
If it was a desktop computer I'd open it up to reconnect the cables that are connecting those components to the motherboard, but since it's a laptop this problem may be because the components aren't working or the BIOS is messed up. Try to set the BIOS to it's default settings, there should be such an option. If this is not working I think you should take the laptop to a service and let the professionals do their thing (it shouldn't be that expensive to fix, free if you have the warranty).