swalker wrote:
I recall that when you insert a WIN7 CD into the CD drive of a machine
that already has Win 7 installed that you have the option of either a
clean install or a repair.

My question is, if you choose repair what does the repair overwrite?

What user data is lost?

Thanks.

On the modern versions of Windows, Windows must be working
and healthy enough to accept a Repair Install attempt.

You insert the disc, and run "setup.exe" off the disk.
That starts the repair install.

The C:\Windows is moved to C:\Windows.old.

A new C:\Windows is made, and the install starts.

Programs and user files are preserved.

A dialog box should alert you to the conditions of
the install, and that Programs and user files will
be preserved once you kick off the process.

*******

Now, because that keeps so much of the original
configuration, it's also not going to be good at
removing malware. If the Repair Install keeps
the registry content (in support of the installed
programs), lots of stuff that launches malware could
still be enabled.

As a result, the utility of doing this, is a function
of what you think this is going to fix. Will it
remove a rootkit ? Probably not. Will it restore
that set of DLLs you foolishly deleted in haste. Yes,
it can put those back. It might even manage, by magic,
to put back your network stack or something. But, because
the process "respects" so much of what was there
previously, there are going to be *lots* of corner
cases it doesn't touch or fix. If a registry setting
screwed up your networking stack, then that registry
setting will still be present.

It's almost like the utility (on Windows) of removing a
program, using "Programs and Features" and expecting
a re-install to fix a mistake or corrupted setting.
Unfortunately, for better or worse, uninstalls don't
clean the registry - it is rare software which has
an uninstall option "remove all traces of settings"
when doing a Remove. Consequently, I cannot (on average)
recommend removing a program and reinstalling it again,
as it achieves almost nothing for the effort. A
Repair Install is similar. There will be some good
cases for usage (such as deleting a set of important
files or getting into a huff and deleting WinSXS or
something), but for the more common problems,
like malware or adware, there's no particular reason
it's going to help.

*******

A "Clean Install", where *everything* is thrown away,
that can fix stuff. But is very expensive in terms
of your personal time, to put everything back the way
it used to be. User data and Programs will be removed,
so you want backups of C: before doing that. As time
passes, you consult your backup of C: and bring forward
your email profile and so on, and gradually restore
things. It takes some people months to complete the
exercise, if done that way (because some people are
pack-rats and they have 500 programs to restore).

To do a clean install:

1) Don't be in a rush.
2) Make a backup of C: and friends.
3) Remove extraneous hard drives not involved in the
installation process. This prevents collateral damage
to the drives that you didn't back up. Your backup drive
should be unplugged too.
4) Boot the installer DVD.
5) Have it format C: and do the install.
6) Take your time restoring email profile and the
rest, using your backup image of C: to access the
files.

On one occasion, I had a Windows installer CD *delete*
the partition table, even though I'd clicked cancel
during an install. And this is yet another reason
for backing up a hard drive, before starting
an install. Just about anything can happen during
an install. Normally pretty safe, but if **** happens...
it can be very messy.

HTH,
Paul