HDD letter designation

I reformatted my HDD and tried to do a clean install of
ME. When I start, the system says Windows requires xxx of
free space on Drive C: The setup is calling the HDD drive
D: and not C: Setup won't let me install to D: How do I
get the system to call the Drive C:? It's the only drive
on the system.

On Sat, 4 Sep 2004 14:30:51 -0700, "steved"

Brace yerself, here comes a "cq definitive" ;-)

I reformatted my HDD and tried to do a clean install of
ME. When I start, the system says Windows requires xxx of
free space on Drive C: The setup is calling the HDD drive
D: and not C: Setup won't let me install to D: How do I
get the system to call the Drive C:? It's the only drive
on the system.

It's helpful to know exactly how drive letters are assigned in the OS
you are working in - which is generally similar across Win9x and thier
DOS modes (and indeed DOS itself), at least where HD are concerned,
but is different in NT such as XP. WinME is a Win9x, of course.

Letters A: and B: are reserved for diskette drives. LS120 drives are
1.44M"shape" but also handle thier own 120M diskettes, and connect via
ATAPI ("IDE") or ?SCSI rather than the diskette interface. If things
go right, LS120 can be seen as A: or B:, but if they do not go right,
it will pop up either as a later letter, or be duplicated as such. If
no hardware exists as B:, then B: acts as "the other diskette in drive
A:", with prompts to switch diskette etc.

Letters C: to Z: are allocated to everything else, and this starts
with whatever BIOS detects and passes on to the OS at boot.

CMOS settings can affect this, if you set something other than the
first physical HD to be the first boot device. This can cause
something other than the HD to be seen as "C:", e.g. a USB stick or
camera, Zip or LS120 drive, drives on S-ATA, SCSI, Firewire or USB,
etc. Optical drives generally aren't a problem here. This issue can
cause huge problems with XP Installs, where C: is not "C:" etc.

When BIOS looks for devices, it generally includes them if the
hardware exists - with the exception of HDs. What BIOS passes to
IO.SYS or NTLDR is not just the HD's physical identity, but the list
of partitions it sees on the drive. A HD with no visible partitions
won't get any letters at all, and volumes that are of unfamiliar type
(e.g. Linux or NTFS as seen by Win9x or DOS) don't get letters either.

MS OSs recognize two broad types of partitions; primary partitions
that may be NTFS, FAT32, FAT16, FAT12 and historical variants of
these, and extended partitions.

Primary partitions may be bootable, and one per HD may be set as
"active", i.e. to be booted. Only the active partition on the "first"
HD (as defined by CMOS) boots.

The extended partition itself is just a container, and has no inherent
file system; that is a factor of the logical volumes within. Extended
partitions are not bootable, although the bulk of a bootable OS may
reside on one of the logical volumes within an extended partition.

Both Win9x and DOS (mode) start from IO.SYS, and IO.SYS assigns drive
letters from C: to HD volumes in this order:
- the first primary partition of each physical HD
- the logical volumes in extended partition of each physical HD
- additional primary partitions of each physical HD

In contrast, NT assigns HD drive letters this way...
- for each physical HD:
- the first primary partition
- the logicals in extended partition
- additional primary partitions
- next physical HD
....and this is itself subject to changes made in terms of drive
letters that can be explicitly set by the user.

Back to Win9x; IO.SYS will then process Config.sys, and this may load
drivers that take drive letters. Then Command.com processes
Autoexec(.bat) and entries there can take drive letters too - it is
here that optical drives take their letters from MSCDEx, if present,
which can set the letter as long as it is higher than those already
assigned to HDs by IO.SYS

If Win9x GUI loads, then Plug and Play kicks in. This will detect HDs
that were set as None in CMOS, and thus adds letters to these after
those that IO.SYS has already assigned. PnP also detects optical
drives that were not already set up (that's the norm, in a well-setup
Win9x) and assigns letters to these after all HD letter assignments.

Other drive types may be detected by PnP, such as USB flash or
cameras, Zip drives and so on. These generally get drive letters
"above" those of the HDs that IO.SYS and PnP detected.

Win9x lets you set drive letters for non-diskette, non-HD drives, but
only above those taken by the last HD volume detected. Some devices
e.g. Zip drives are notorious for butting in and taking the first
letter after the HDs, so it's often useful to reserve a letter for
these by pegging the optical drive higher. Note that whenever a new
optical drive is detected, the letter assignment you made is thrown
away - unlike those set via MSCDEx in DOS mode.

You can map LAN shares to drive letters, and if you do, these can
obscure actual physical drives. This is often a problem in old Novell
Netware installations, which use F: in this way, thus masking any HD
volume that might be F: otherwise.

A note on Win9x EBD, which creates a RAM disk at boot and then sets up
optical drives. If no known HD partitions are detected, then the RAM
disk becomes C: and the opticals start from D: onwards. The logic in
the EBD's Autoexec.bat will see and fret about this ;-)


Back to your case: Why would WinME's Setup.exe see your HD as D: and
not C:? I'd guess it's because your HD is set as None, so that IO.SYS
doesn't see it until it's seen something else (CD? RAMdisk?) as C:
first. Check CMOS HD definition, CMOS boot order, make sure no USB
drives are plugged in, and re-try.



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