create new user ID
I cannot explain it but have observed the effect three or four times.
Create a new user and try it out (log off the old one do not "switch" user). I have seen huge performance improvements on old Vista/7 machines.
If you like it, move all the data over to the new user folders if necessary.
After a while to make sure nothing has been left behind you might delete the old user and user data folders.
Takes about 5 mins to try it out.
Please report back if you test it.
I "discovered" this when I was fixing a machine with a broken user profile. User could not log on at all. Machine was back to as-new performance. It has previously exasperated me that Windows PCs seemed to gradually slow down over time with no visible reason or cure. I have repeated the excercise a couple of times more and it has "worked" in each case.
Some applications such as email clients or iTunes might need some work to get the data across.
Some applications offer the option "install for this user/all users" I have always chosen "all users". If you have some applications installed for one user then you will need to consider that.