I have Chessmaster 10th edition on XP and I must say it is fantastic. It is stronger on the hardest difficulty setting than I think I will ever be and has hundreds of personalities at various levels of chess ability, a good personal training system and an extensive opening and game library. There is a limited demo available which might be good to test against Vista.
http://www.download.com/Chessmaster-10th-Edition-demo/3000-7562_4-10297913.html
I thoroughly recommend it.
well with a computer it always plays good moves the rating just determines the random mistakes they make or moves they miss to equalize to their rating in my opinion.you just have to learn to spot the mistakes they make.