[Discuss] How do Linux guys back up Windows?

[david at thekramers.net (David Kramer)]

I am now in the odd situation of having two computers that are dual
boot, and that I use under Windows more than I have in the past (which
is to say a couple of times a YEAR).

Under Linux, I know that I can always reinstall the OS without hassles
and the update it, so I usually use scripts to just back up the
configuration files and documents and mail, etc.  A big server takes in
the neighborhood of 17GB to back up this way, which is great.  Windows,
on the other hand, is more than a collection of files.  It has magical
things in special places, and a registry that Must Be Right.  It also
can't be taken as a given that if my system dies, and I need to (say)
replace a hard drive, that I'll be able to use install media to
reinstall the OS.

My normal MO is to back up to external USB hard drives that are normally
disconnected and sitting in a drawer.  In preparation for this I bought
a 1TB one to supplement my current 500GB one.  I'm thinking I'll use the
1TB one for Linux and the 500GB one for the two Windows instances.  I'm
not sure if that will be enough, though.  I did a test Windows Backup on
my desktop Windows instance and it took about 180MB, which was a pretty
big surprise.  I later learned it does diffs after that so it shouldn't
grow very fast.  Still I don't know if 500GB will be big enough for
both.  Maybe I can switch to a program that stores backups compressed,
since I'm not really worried about speed.

Let's say I already have my personal documents backed up through
synchronization, but I would like to not have to reinstall all my apps,
especially Office.  Given all that, how would you recommend I back up? 
Are there any good (free|cheap) programs that will back up Windows to
external hard drives?

Thanks.  I know this isn't really about Windows, but I know a lot of you
are SysAdmins that work with both.  I also wanted a Linux perspective on
this, because a lot of the Windows-only SysAdmins I've spoken to left me
with the impression that they don't think about it very much and just do
what they're told by Microsoft.