I built a brand new core2duo in October of 2006 with XP. Recalling from memory it had 1 gig of ram,(maybe 2 ??) NVidia GTX 7600, its hard disk size I do not remember as this pc did not last long. My wife at the time was not happy at the price tag which was $1300 after everything (I already had a monitor) CRT style. Very good gaming PC. Not freaking awesome like yours, but hey it can run WOW, battlefield 2, and other mid 2000's decade titles very well.
I also bought a laptop for school early that summer in 2006 which was a full Pentium M 1.5 ghz, 512 megs of ram (later upgraded to 1 gig), and a 80 gig hd. That was $800. Probably closer to $950 after I put an additional 512. This was mainstream priced computer and specs in the time of Vista.
Neither touched Vista for good reason.
Remember that Joe six pack looks at price tags. If it is over $800 he wont buy it etc. Maybe $1200 for a Joe six pack who works in a cushion office job where he has money and needs extra software.
So it is not unreasonable to bash MS, not the OEM's on this. You could not get a reliable cheap PC for the price point the market could bare to run Vista until about 2009.
My old core2duo would run Windows 7 fine. However if it had just 1 gig of ram it would have trouble actually running software after the boot. The board was plagued with bursting capacitors sigh.