My Disk Cleanup isn't working, can it be fixed?

[KatyMac]

It starts fine then hovers around System Error Memory DUmp Files for several hours before I give in & cancel it

Any ideas?

Does this happen while it is calculating how much space can be freed up or is it while it is compressing and removing files? As it is showing you file names I imagine it is the latter.
How much free space is on the drive you are cleaning? Machine does need some free space to work in.
I'm no expert but you could try going through what you have on the machine and removing (largish) files you know you don't need, emptying the recycle bin and maybe also clearing browsing history using whichever internet browser you use.
If that doesn't help it is also possible that you have corrupt registry entries where something like Ccleaner (free download) could help. That would do a cleanup of all your temp browsing files too.

Yes it as that

I removed the 'SIMS' dd's friend had loaded & then tried again & it worked fine