From: "Rich Gauszka" 

Given the option  I prefer a clean install even with an upgrade. I also
wonder how the upgrade version of Vista will hande a drive failure/OS
reload?

 http://blogs.zdnet.com/Ou/?p=414&tag=nl.e589

In the past, Microsoft has always respected their customer's time and
allowed upgrade versions of Windows to install on a fresh machine so long
as the customer could provide proof of possession of the old software. 
These new Vista Upgrade DVDs which I'm assuming have already been stamped
out will lack the ability to install on a system unless Windows XP or 2000
was present.  This means anyone looking to do a fresh install for any
reason will not be able to.  Someone who is doing disaster recovery after a
hard drive failure or a virus infection won't be able to wipe their hard
drive and install Vista, they'll have to install XP first and then install
Vista on top of XP.  That could easily mean nearly an hour wasted.  If
you're paying someone to rebuild your computer, this will mean an extra
hour of labor that will be billed to you for the installation of Windows
XP.  Will Microsoft pick up the extra hour tab from Geek Squad for
everyone?

Some might just say tough; you don't have to buy Windows Vista Upgrade
Edition if you don't like the terms of the agreement.  But the problem is
that there are probably already millions of people who bought in to the
promise of Vista upgrade coupons during this last holiday shopping season
with their new computers or their copy of Windows XP and they weren't told
that the upgrade terms have been changed.  The Vista Upgrade coupons were
used to lure people in to buying brand new computers for the holiday 2006
shopping season when many people would have probably opted to wait until
after Vista launches at the end of January had they known about these new
restrictions.  Now these people are going to be in for a big shock after
they wipe their computers and find out that their copy of Vista won't
install without XP on the computer.

So why is Microsoft making a bone headed decision like this?  One
possibility is that Microsoft is afraid that people might try to keep
running XP or Media Center on their existing machines and use Vista on a
new computer.  This would mean that Microsoft would be giving away two
copies of Windows for the price of one

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