Also remove all but the last 2-3 restore points.
Use Windows DiskCleanup program
Many of the $NTUninstall........... files in Windows folder can be removed, sometimes blue colored, but keep this one $hf_mig$ because it keeps a list that update checks I think. Sure don't want it all to download again.
Empty Recycle Bin
Run a Search for all files over 10 MB in size, aka 10000 KB. See if any of them can/should be removed.
Run a search for all "temp" and "*.tmp" folders and files.
Empty all browser caches
Empty all email Trash folders
If you don't use hibernate, then turn it off, which should get rid of the hiberfile.sys, but if not, delete it afterwards. (ignore on W8 unless you turn off Fast Boot).
Remove any backup Service Pack files if you aren't going to revert to before it was installed.
http://www.optimizingpc.com/optimize/deletefiles.html