I used Teracopy to duplicate on non-system partitions some folder parents such as
$hf_mig$
ie7updates
Hewlett-Packard
ServicePackFiles
I386
My Music
Then I deleted the originals from C:\, trimming C:\ down by 2 GB.
Then I replaced the original parent folders with Reparse Points that redirect to the new locations.
Reparse points implemented with the Junction Point option in the free version of xplorer2_lite.
There are other tools that can do this.
I have NOT relocated stuff that is :-
Often needed and would have degraded performance if held in a partition remote from C:\; or
Is needed for Booting up or otherwise essential for adequate operation.
(I use the H-P printer twice a year)
I am confident of my partition backup images that if all partitions are wiped out then :-
I only need my Boot CD to restore C:\,
I then have a free choice of restoring the other partitions from either the Boot CD or under Windows using only C:\.
I have not needed to fix the registry.
The only applications to recognise the changes are :-
my Defragger which no longer thinks that I386 etc needs defragging when C:\ is defragged, and
Partition Imaging (Acronis and Macrium) which carefully capture the Reparse Point linkage but exclude the relocated files.
I suspect that CCleaner will NOT be like Acronis etc.,
and will act as if the relocated files are still present on C:\ and will clean them.
Regards
Alan