I just added new hard drive to a tower. I moved the old drive with windows
on it to slave and installed XP pro on the new drive. Everything looks dandy
but the new boot drive is labeled F: and the old drive C:. Is this going to
cause troubles for me later on, and can I or should I bother to change it? You
did a version of this before, but I wasn’t sure if C was sacred, or if new
software that needs to monkey with Windows can figure things out like that by
Well, there’s actually two answers to this: yes “C:” is sacred, and no, it’s
I know, that wasn’t very helpful.
But I do have some practical advice and some bad news about changing what
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“C:” is not supposed to be special any more, though once upon a time it was.
When hard disks were first added to personal computers A: and B: were assigned
to the floppy drives, and C: was the hard drive. In fact, C: could be counted
on to be the hard drive, the boot drive, and the drive containing the operating
But it’s been quite a while since that was a valid assumption. As you’ve
seen today other drive letters can now end up as the boot/Windows drive, and
things pretty much work.
The risk, of course, is some software making an incorrect assumption that C:
is the Windows drive. Fortunately those situations seem to be infrequent, and
getting more so.
Advice #1: If it ain’t broke… don’t fix it. As we’ll see
in a moment fixing this gets painful. Things should work just fine with the
setup you have. You may have a mental hurdle to overcome in remembering that C:
isn’t the boot drive (I know I would), but unless you run into a problem that
can be traced to the drive assignments, I wouldn’t change a thing.
assigned to your Windows drive is to reinstall Windows.”
Advice #2: Pseudo-standards are good. When you build out a
new machine I do recommend, if you can, making sure that you end up
with a system that has its boot drive as C:. As I said, it shouldn’t be
necessary, and it’s not really a “standard”, per se. But it is one of those
things that can make life a little easier in case you do run into situations
where some software makes a bad assumption. Given that 99% of the machines out
there are configured this way, it’s just a safer thing to do.
Sad Reality #1: Change is painful. Changing drive letters is easy – as
long as you’re not talking about the drive that holds Windows. In my opinion
the only safe way to change the letter assigned to your Windows drive is to
Here’s the problem: installed software, including Windows itself, will have
been configured to whatever the Windows drive was when they were installed.
Using your example, by that I mean that in various configuration files
including but certainly not limited to the registry will be references to F:.
Lots and lots of references to F:. Unfortunately changing the drive’s letter
assignment won’t go through and find and change all those references to the old
If you do successfully change F: to C:, then a lot of things are likely to
stop working. In fact, I’d actually be shocked if the system even booted.
Now, one could argue that you could just scan the registry for all
references to F:, change them to C:, and be on your way. It wouldn’t surprise me
if there were tools out there that do this for you. And it might even work in
many cases. The problem is that frequently the registry is not the only place
information is stored. Let’s say that some random application you use is
configured not to use the registry and stores its own configuration data
itself, in a proprietary format. You may be able to fix it when you run the
application, but you may not. And it’s an annoyance in any case.
That’s why I say that the safest way to reassign drive letters
involving the Windows drive is to reinstall. That way everything is configured
properly from the start.
I’d love to hear some reader’s experiences on this topic. As you can tell,
reassigning the Windows drive letter is something I actively avoid.