Welcome to HH Chief. Thanks for the informative post. A few things to note about the forum, there is a bunch of bars under everyone's avatar, the more posts you have the more bars you have. Points are a newish thing and basically you get points for posting and for people replying to your post directly. Under that is a join date.
Not to say that people with a low number of posts dont know anything, you obviously know things as you posted some information, but take the newbies posts with a grain of salt when they talk like they are 14 years old and their first OS was Vista. There is nothing wrong with xp and the solution you provided is a nice fix as sometimes installing and uninstalling mouse drivers especially switching companies can end up removing an entry like that and cause some trouble.
With your setup, windows 7 will be ok as you got plenty of RAM and the superfetch in win 7 will make things seem really snappy. If i were you i would go and make sure you turn off indexing in windows 7 otherwise your hard drive will be clicking and groaning non stop. Indexing is only good if you have tons of files to search through and you have to search for stuff all the time. For 99% of people they dont need this and it will net you about a 5% increase in performance.
I still proudly run XP and i have it tweaked and it runs really quick on my aging rig, and imo much better than win7.