Problem accessing DOS prog. & Registry.

The following error display when i try to access any MSDOS program "This program cannot be run due to restrictions in effect on this computer Please contact your system administrator". I did not touch any program nor registry that would change the system configuration. i just wondering when the next start up of the system the following error generate. I cannot also access the REGEDIT program. What will i do to return to normal state? without reinstalling the windows OS?.

thanks.

holden