whwenever i try to copy file frm cd to harddisk, it gives error saying...

"Cannot copy <filename>.Invalid MS-DOS function"

wht do i do to copy this file???

Try cleaning the CD.

As Wilhelmus suggests, clean the disk. If that does not resolve the problem, you are left with two possibilities - the file on the disk is corrupted or the CD rom has begun to fail.

Try the disk in another computer and see if the same message is received. If it can copy the file, you know that the file and the disk are fine, and you probably have a CD rom that is failing. If it too fails to copy, the file on the disk is probably corrupted.

That is half the problem. If your CD rom is the drive that was used to burn the disk originally, and it can copy from the CD rom to the hard drive from other disks you've made, it is possible for that one disk there was an overburn that causes it not to be able to be read. If your CD rom cannot copy other files from other disks to the hard drive, then you may need to replace your CD rom.