hi iv got a samsung r520 laptop and iv gone to boot it up im on windows 7 and when i boot up its saying systm operation not fo

Do you have any flash drives or disks in the system? Remove them if you do and try again. Check the BIOS to make sure the hard-drive is seen.
Would be a good thing to list some more details about the issue like when it started, did you do anything to the system before this issue started, what you tried already, etc...