Microsoft have published a good intention for System Restore, which is that :-
1. It ignores user documents etc so they do not lose their recent edit corrections,
2. It restore the system files so Windows will behave as it used to behave before Patch Tuesday or whatever else damaged it.
In practice there are grey areas where it cannot decide in which category the file should be.
Often a Restore Point is automatically created without permission or notification, so I have no chance to first use CCleaner.
DO NOT EVER use Restore Point to go back UNTIL you first use CCleaner.
If you fail to use CCleaner then the Firefox and Java caches are not purged.
These caches are in the grey area - Windows does not know what to do.
What it does is look at the latest ??????\cache etc that is in your user profile,
and look at the earlier version within the Restore Point and realise they will not fit together,
so by some mysterious unknown and possibly random mechanism it allocates an extra (2) to the name of one of them.
This is where many of the extra (2) files come from.
I forgive the occasional difficulty that UN-intelligent software has in making a perfect decision, and that the best thing for it is to make both versions available for a subsequent user choice.
WHAT IS TOTALLY UNFORGIVABLE is that it does not GIVE me information upon what it did;
instead it gives me a glimpse on the screen of the location where 2 files exist, and which came from what;
BUT there is no means, other than pencil and paper, to record this so I may take any corrective action,
and once the computer has booted a search for files created in the last 5 minutes does not get that information.
Please forgive the rant, but in this modern internet broadband era, if computers require pencil and paper we might as well go back to the "good old days" when we communicated with quill pens - or for speed we went to the railway station for a clerk to punch it into a telex machine !!!
O.K., rant over. This is how System Restore creates spurious (2) files, and there are no clues available to guide the user in which to keep.
This demonstrates that System Restore has admirable intentions, but less than competent execution.
I am sure that Microsoft have tried to improve System Restore, and the continuing problems suggest that even with all their resources, and all their designers private knowledge of what they created, every attempt to fix one thing inevitably leads to breaking the software in a different way.
If M.$. cannot fix it, what hope has anyone else.
If CCleaner should have a go at it I think these forums will be overloaded with requests for help from people who "gave it a go".