When would be the best time between now and January 14 (when Microsoft stops supporting Windows 7) to buy a new computer?
The week after Christmas is probably when prices will be best.
But if you are particular about the specs of your rig, post Xmas sales are often full of the machines that nobody really wanted.
If specs are your thing, then maybe now, since it is pre-black Friday and vendors are stocking up.
However, if you have been squeezing the last drop of life out of a Win 7 machine, probably anything you buy, even from the clearance shelf, will probably blow you away.
Build your own. Save 35-50%. Anyone can do it now, plenty of "PCs for Idiots" guides out there. Its pretty much just snapping the pieces together now. Newegg sells the stuff and shows you how to do it.