"Easily? If you have a good solution for cutting these down without breaking the various installers and rollback points I would be very interested!"
These steps will eliminate a lot of the garbage that Windows and apps have accumulated:
1. Delete the Windows crud. Go to Computer, right-click on your drive, and select "Properties". Click on the "Disk Cleanup" button and wait a minute while it scans your drive. If you get a "Clean up system files" button on the summary screen, click on it and wait another minute while it does a more thorough scan. Select all of the items on the summary list, then click on "Okay". Confirm the deletion of the files.
2. Delete the application crud. Install a utility like CCleaner or Wise Disk Cleaner, let it scan your drive, and then tell it to delete the accumulated debris.
3. Delete your temp files. Go to C:, Users, your user profile folder, AppData (you may have to enable the display of hidden files), Local, Temp. Delete all of the garbage there.
4. Delete the system temp files. Go to C:, Windows, Temp. Delete all of the garbage there.
5. Remove the hibernation file. If you don't hibernate your computer, launch an elevated Command Prompt (right-click and select "Run as administrator"). Run "powercfg -h off".
6. Reduce the size of system restore points. Go to Control Panel, System, System Protection. Select your drive and then click on "Configure...". Reduce the "Disk Space Usage" to something more reasonable (I usually set it to 1%). You can also delete your existing restore points at this screen to free up more space.
7. Delete the backup copies of Windows patches and updates (optional). Go to C:, Windows, SoftwareDistribution, Download. Delete all files in that folder.
FYI - Unless you've told it otherwise, the Windows page file will reserve a chunk of disk space equivalent in size to the amount of memory in your PC.