I wonder whether I'm the only one that didn't have these files [mouclass.sys and mouhid.sys in drivers folder in system32 directory] updated after Service pack 1. Can some one please check.
Um, you'll notice that most system files are not updated by SP1. This is because most system files are not supposed to be updated. There wasn't a mouse driver hotfix to SP0, so the mouse driver files were never a part of SP1.