Hi Leabank,
Are you aware of any changes made to the computer prior to the issue?
Usually this error message occurs if in the BIOS the booting is set to start from CD Rom or floppy drive as first boot device. Whereas you are trying to boot from the Hard disk. If you have a CD in the drive be sure to remove that so your PC does not attempt to boot from the CD.
Go into the BIOS setup and change the Drive Boot Order, so that the Hard Drive comes first as a boot priority. You should be able to boot into Windows normally after you save these configurations.
Note: Modifying BIOS/complementary metal oxide semiconductor (CMOS) settings incorrectly can cause serious problems that may prevent your computer from booting properly. Microsoft cannot guarantee that any problems resulting from the configuring of BIOS/CMOS settings can be solved. Modifications of the settings are at your own risk. For help with the BIOS settings, refer to the computer manual or contact the computer manufacturer.
Hope this resolves the issue. If the issue persists, you can write to us and we will be glad to assist you further.