You are skating on very thin ice when you try to remove anything to do with Windows, excepting the old Update Files that you have already removed.
As far as I know, W Installer is the part of Windows that assists you installing new Software. Definitely a No-No.
I am assuming that you haven't found any Programs that are no longer needed and that you do not have an External Hard Drive that you can use to store rarely used Files or Movies.
I use a WD 'My Passport' 1TB USB3 Drive, that cost me about £50.00. I don't actually have USB3 on my 8year old PC, ex-XP 'updated to W7, but it will keep me in Backup-space as well as my stored Movies, for a good few years yet. As well as keeping my 500GB HD fairly lean.