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It depends on what external device you're talking about when you're talking about the destination for your file, but the error messages give us a clue.

I can't copy files from my computer to external sources. I'm using Windows XP Professional and an Intel Pentium 4. The first time I attempt to copy a file to an external source, every time I try, a dialog box always pops up saying it is either the file is already opened or the source is write protected. But I can copy the file within the system. I'd be very grateful if you can help me.

In this excerpt from Answercast #57, I look at problems in copying files to external media.

Copy errors

Well, I do want to clarify one piece of terminology. "Source" has a very specific meaning and you're using it backwards.

"Source" is where the file comes from. It's the destination you're having problems with.

So for example, if you're trying to copy a file from Drive C to Drive D, "Drive C" is the source; it's the origination of the file. And then "Drive D" is the destination.

So, I'm going to assume that what you really mean throughout here is the destination - wherever you're trying to send that file to is where a problem is arising. And your symptoms match that; the fact that you can copy a file around on your original hard disk does imply that whatever is going on here is related to the destination.

File in use

Unfortunately, the error message is very, very generic and it doesn't really give us a whole lot to go on.

Certainly, if the file is already open, you can use a tool like Process Explorer to see who has the file in use. In fact, I have an article on that, "Who's using a file in use?" that I'm going to point you at.

That will walk you through using Process Explorer to at least try and identify if there is a program that has that file in use.

In the sense that this is a destination-related issue, it is possible that you are attempting to overwrite a file on the destination - and that destination file is itself in use - which would essentially give you the same result. If that destination file is in use and you try to overwrite it, you can't because it's in use.

Is the destination writable?

The other approach is: we do need to double check to make sure that, in fact, the destination you selected is a place you can write to.

I would suggest you try and create a file there by some other means... not related to the file you're copying. Just a create a temporary file.

Fire up Notepad and create a file with a brand new name in one of those remote locations. It is possible that you're dealing with read-only media. If you're trying to save to something that is fundamentally read-only (like a CD, a read-only CD)... well, you can read files from it all day long, you just can't write to it. When you try to write to it, this is exactly the kind of message that you'll get.

Similarly, if you have a network drive, it is very possible that you can connect to it in such a way that you only have "read" permission. You can read all you want from it, but any attempt to write to it will cause the error messages that you're seeing here. And so forth.

It really depends a lot on exactly what external device you're talking about when you're talking about the destination for your file. But those are the kinds of things I would have you look at. Those are the kinds of things that can get in the way.

Article C5868 - September 30, 2012 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

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1 Comment
October 5, 2012 4:26 AM

Microsoft now has this BitLocker drive encryption software on some of the high-end versions of Windows 7. When you use it, you can read and write to your hard drive and shared drives on the LAN, but you can only read from external sources -- you're prohibited, for instance, from saving a file to an attached USB stick which is not also encrypted via BitLocker. Could this be what the question was about?

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