Ways to free up 12 GB from C: ?

‘d like to copy my C: drive to an external drive with 12 GB less space.
I’m stumped . . . but I believe it can be done.
When I look at top-level Folder Properties, I find very few over 1 GB – target drive has 76 GB, existing C: has 88 GB.

Would appreciate any ideas.

I’ve run DIsk Cleanup & used CCleaner.
I tried compressing one folder of pictures, but hardly any gain.
I’ve looked for Microsoft Update files named *KB* but can’t find any.
This is XP Pro