No, they're not only different OSes, they're different installations
and different instances of OSes. You can even have 2 or more
clones of the same instance of an OS resident in the system at
the same time without interference between them. The only
difficulty that arises is when a clone is started up for its first run
and it sees its "parent" OS. Then it can create sporadic shortcuts
to files in its "parent's" partition for files it should contain itself.
But after that first startup, the clone can see its "parent" in
subsequent startups without any problems. (The "parent" can
always be allowed to see its clone at any time without a problem.)
The only "problem" would be if the installer for the new OS
could see the partition for the old OS when it did its installation
for the new OS. It then wouldn't tell the new OS that its partition's
name was "C:". It would tell the new OS to call its partition "D:"
(or some other letter, depending on how many partitions it saw).
If you want your new OS to call its partition "C:", disconnect the
old hard drive before doing the installation of the new OS on the
new hard drive.
If you want to dual-boot the 2 OSes after installing the new OS
on the new HD while the new HD is isolated from the old HD,
just run msconfig from the new OS, click on the Boot.ini tab,
and click on "Check all boot paths". Msconfig will then add an
entry for the old OS in the boot.ini file on the new OS'es
partition. You may have to set the timeout time explicitly, though.
If there are no other partitions on either HD, you can assume
that the single partition on each HD will be (in effect) marked
"active", and it will have the files necessary for booting.
Besides using the boot menu to choose between OSes,
you could let the HD's position in the BIOS's HD boot order
control which HD got control at boot time. (The HD boot
order is *not* the DEVICE boot order). You can do that by
making the chosen HD the Master on IDE channel 0 - to take
advantage of the *default* setting of the HD boot order - or you
can place it at the head of the HD boot order via keyboard input
to the BIOS at startup. Each HD, when it boots, will have the OS
which is resident on it as the 1st entry in the boot menu and as
the default OS to be booted in the case of a timeout.
Don't worry about the old OS calling its partition "C:" when it's
running. When it's running, it will call the new OS's partition "D:"
(or some other letter), but that should not be a problem unless you
have shortcuts on the old OS's partition that refer to some other
existing partition as "D:". Otherwise, having 2 or more OS's in
the same system each refer to its own partition as "C:" is not a
problem (despite what some "experts" may claim). I have at any
one time 4 to 10 OS's in the same system, and each calls its own
partition "C:" when it runs, and it's not a problem.
*TimDaniels*
