Free Upgrade To Windows Vista?

I build new computer systems and every so often I have enough spare parts
left over, plus a few new parts to build myself a whole new computer system.
I was going to wait until the release of Window Vista until I saw this ad,
"Get a FREE upgrade to Windows Vista when you buy a qualifying copy of
Wondows XP today. It goes on to show that if you buy XP Pro you get a free
upgrade to Vista Business. I got the Xp Pro today and a redemption coupon
which has the FINE print. It spells out requirements that have me worried.
Number 1, I have to provide a receipt for a PC PRELOADED with Windows XP
Professional. Why would I buy an OEM CD copy if the thing is supposed to
come preloaded? Number 2, I must provide a receipt from the period October
26th to March 15, 2007. I can say the 85% of the parts fall in that period.
Number 3, it must be from an authorized system builder! Are there any
system builders that are not authorized? ;-)

Am I worrying needlessly or should I just return this Window XP Pro with the
coupon asap?

Al