I've got 23GB free on this laptop and Symantec EndPoint Protection Small Business 12.1 keeps insisting I need to run disk cleanup to free some disk space.
I found this recent Symantec post that talked about proxies causing that problem
but I don't think that applied on this site
I then found this old (!) 2008 post talking about the same problem with Symantec EndPoint 11.02 and how to fix it by removing the check from the registry
except I couldn't find that value in my registry.
I did work it out in the end, I'm on 64 bit Windows 7. The equivalent location to check in the registry is
where I found the entry for ALUAlert and deleted it :-)
I did also note that in the Control Panel under Symantec LiveUpdate Settings > Update Cache, the max cache size was only 10MB so I bumped that up to 100MB.
Only thing is I don't know which fixed it now :-(