I am using a registry cleaner and doing an aggressive scan. The report has shown up Invalid ProgID entry's (OLE/DDE) and
Invalid ApplD entry's (OLE/DDE)

What are these and how safe is it to remove them?

I think these are mentions of programs that were uninstalled but traces were left in the registry.

If you have a good registry cleaner, it will do a backup of your registry before making any changes so if it does go wrong, you can just restore from the backup.

I personally think you are OK to remove these but lets see what some others say first.

Hi,
As the previous answer stated, your Registry Cleaner should be making backups of changes; that you can later put back if you need to.
I would let it delete what if finds.
Best wishes.

Thanks loads LTheobald and fredg, I have done an aggressive registry clean and everything seems fine. Cheers!