C:\Windows\Downloaded Installations\

These folders contain the setup files of downloaded and installed applications and Windows updates. The last one contains the downloaded Windows updates, which are there in strange names without any extension. With most of those files you can add MSI or EXE and run them separately. Saving these files makes it possible to patch them on another Windows system or Windows setup files.

IOW, it's OK to remove these files, as long as your Windows install is stable and working as it should. I would not, however, remove the folder, as installation files from future updates to Windows will be stored in that folder.

You can read more at http://www.optimizingpc.com/optimize/deletefiles.html.