Floppy Drive error

Hi
I am using win95 on a old 486 pc and every time I try to copy a file from the a:drive the following errors have come up.
“cannot copy xxx (where x is the file name)
the system cannot read from from the specified device,when clicking ok it comes up with the following “this program has performed an illegal operation and will be shut down.When clicking on a exe file on a:drive it comes up with the following.
“this operation has been cancelled due to restrictions in effect on this computer.please contact your system administrator.As I have had no problem before
copying from a:drive I’d like to know whats wrong.
Thanks
Leslie