Hi, Doug.
It's not a stupid question. But confusing use of some common words in
technical contexts makes a simple idea hard to explain.
For example, "drive" means different things in different contexts - just
like "right" can mean the right hand, or correct, or "the right stuff",
and "left" can refer to the left hand or to what we left behind. A
"drive" letter never refers to a physical hard disk drive, but to only a
primary partition or to a logical drive in an extended partition on that
physical drive. And "drive" letters can also be assigned to other
devices, such as optical drive, USB flash drives, or even digital cameras.
When we say that each operating system (WinXP or Vista or Win7 - or
multiple installations of one of those) must be installed on a separate
'drive", we really mean a separate "volume"; while often called a
"partition", this actually can be either a separate primary partition or a
separate logical drive in an extended partition. And a different volume
on the same HDD works as well as one on a different HDD The use of the
term "volume" is increasing and that helps to reduce the "partition" and
"drive" confusion, but only slightly.
When Windows Setup runs, it installs Windows in TWO parts; one part is
huge, the other is quite small. The big part goes into the X:\Windows
folder on whichever volume we choose; this becomes the "boot volume" and
is the one we usually think of when we say we "installed Windows onto
Drive X:". This can be any volume on any HDD in the computer. But, no
matter where we put the boot volume, a few files MUST go into the "system
partition", which is the one that the computer uses to start up and to
find Windows - or another operating system - in the first place. This
system volume is the Active (bootable) primary partition on the HDD
designated in the BIOS as the current boot device.
The definitions of "system volume" and "boot volume" are counterintuitive
to common usage. As often said, we boot from the system volume and keep
our operating system files in the boot volume. See this KB article:
Definitions for system volume and boot volume
http://support.microsoft.com/kb/314470/EN-US/
In the typical Windows installation, Drive C: is the first (only?)
partition on the first (only?) HDD, so all this is handled automatically
and silently. But when we start to dual-boot, the definitions and
distinctions become critically important.
The dual-boot system for Vista changed from the method used in Win2K/XP,
and Win7 continues Vista's system. At power-on, the computer finds the
first physical sector on the HDD designated in the BIOS as the boot
device; this sector holds the MBR (Master Boot Record), and it holds the
Partition Table, which points to the System Partition. The first physical
sector of the System Partition tells the computer to find the file bootmgr
(no extension), which uses the BCD (Boot Configuration Data) in the hidden
\Boot folder to choose which OS to load and run, and where to find that
OS, which may be in any volume on any HDD.
So, even if you install Win7 into the second partition on your second HDD,
the boot process will still start in the first partition of your first
HDD. It will present a menu from which you can choose Vista or Win7. If
you choose Vista, your second HDD will be "just another HDD" and its
partitions will be just data drives, so far as Vista is concerned. But if
you choose Win7, then bootmgr will load and start Win7 from wherever you
put it, and your first HDD will be just another HDD - EXCEPT for the first
partition, which will still be the System Partition, because that's where
the critical startup files for the whole computer are.
If you install Win7 by booting from the Win7 DVD-ROM, Setup will not know
what drive letters have already been assigned by Vista. Setup will assign
the letter C: to the partition where you choose to install Win7, even if
that is the second partition on the second HDD. Then it will assign the
next letter (D
to the System Partition. When you boot into Vista, its
operating system files will still be in C:\Windows; when you boot into
Win7, Vista's OS files will be in D:\Windows. This will not confuse the
computer at all, but we have become accustomed to the idea that the first
partition on the first HDD is always C:, and some users have trouble
shaking that mindset.
If you install Win7 by booting into Vista, then inserting the Win7 DVD and
running its Setup.exe from the Vista desktop, Setup will see Vista's drive
letters and will respect those. So, if you tell Setup to install Win7
into Drive E: (the second partition on the second HDD), then Win7's boot
volume will become E: and all those GBs of operating system files will go
into E:\Windows. You will still see all of Vista's operating system files
in C:\Windows, and all your data will be in folders with the same drive
letters in both Vista and Win7. You can use Disk Management to change any
drive letters you like, of course, except for the current System and Boot
volumes, which can be changed only by running Setup again - which means
reinstalling the OS.
where I have Vista installed??)