When turning on my compaq laptop I get a message stating Non-System disk or disk error replace and strike any key when ready

SOURCE: non- system disk or disk error

This means it cannot read the HDD in the machine. Have you left a disk in the CD/DVD slot or a usb drive in one of the usb ports?

You may have to insert your operating system disk in the CD/DVD drive and do a repair installation.

SOURCE: non-system disk or disk error

Your laptop isn't seeing your hard drive to boot up the system. You need to replace the hard drive.

SOURCE: non-system disk or disk error replace and strike

You need to correct this problem in the BIOS. Sounds like the BIOS is not enabling this device you are trying to use. Reboot computer, press enter, or F1,F2 repeatedly to get there.

SOURCE: Message appears : Non system disk or disk error

a) You have a disk in the floppy drive or CD and the computer is trying to boot from that drive. Remove disk and reboot computer. Or ...
b) Your hard disk has failed
Or ...
c) Your operating system is damaged.

SOURCE: non system disk or disk error replace and strike

Your computer is not seeing the harddrive.....Probally isn't working anymore.You need to take youe pc to a certified repair shop and have your harddrive tested.