We routinely use our STORServer 400/500 platform in an environment of this
size: Windows 2000 Server on Intel Dual (or perhaps quad) processor, 1 GB
memory and ~300 GB or so of disk space.  We use AIT2 (currently) tape
technology and have plenty of time for reclamation, etc.  This configuration
works well for us.

I also know of a another site that uses a quad Dell Xeon 700 Mhz system to
backup about twice as much daily as you suggest.  Their tape technology is
STK 9840 which is considerably faster than AIT (and practically anything
else for that matter).  Works fine.

So, yes, you can handle fairly large environments with a Windows platform.
And depending on how adamant you are about staying with a platform,
independent of scalability, you can always add another system and split the
load.  Although that shouldn't be necessary in this case.

Kelly J. Lipp
Storage Solutions Specialists, Inc.
PO Box 51313
Colorado Springs, CO 80949
lipp AT storsol DOT com or kelly.lipp AT storserver DOT com
www.storsol.com or www.storserver.com
(719)531-5926
Fax: (240)539-7175