Invalid MS DOS Function

This post was published 9 years, 3 months ago. Due to the rapidly evolving world of technology, some concepts may no longer be applicable.

I came across an interesting oddity today. When I went to play a video file, after copying it between two partitions on the same hard drive, the first part played fine, but it reached a particular point where it almost completely froze the machine. At this point, the hard drive light was consistently on (not even flickering), and the computer was essentially unresponsive. Even the video program could not be closed (although, it was somewhat responsive). After about a minute, functionality resumed. Repeating this sequence multiple times confirmed that the error occurred in the same location in the file. Additionally, the file could not be moved or copied, with each attempt yielding the error ‘Invalid MS DOS Function’.

The solution to this problem was to run a Check Disk (aka scan disk/chkdsk). While this can be run through a command prompt (and might even have run automatically at system restart), I found it easiest to simply run it from ‘Error Checking’ under the tools tab of disk properties. The necessary options were BOTH: ‘Automatically fix file system errors’ and ‘Scan for and attempt recovery of bad sectors’. On a 30GB partition, this took about 10 minutes to run (with some parts running very fast, and then long pauses at certain files). During the running of check disk, the hard drive usage was quite high (although CPU usage was minimal) – and the machine was quite sluggish (as expected). Subsequent to the completion of the process, the file played without any issues, although there was a barely noticeable (< 0.5s) break in the video (which was soon fixed up).

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