ISO file has mysteriously split into two files 1 & 2

I'm hoping someone can helpl me with this very ISO problem.

All my ISO files (for games) on my back up drive have mysteriously
split into 2 files and renamd to "1" & "2". They are also invisible to
DAEMON tools.

I have renamed them both to "1.iso" & "2.iso" and DAEMON tools can now
see 1.iso (still can't read 2.iso though).

When I browse the virtual disc for 1.iso, I see the files and folders
as normal. I then run the setup file and get the usual install screen
with the graphical interface etc but then closes and the game
installer says install interupted.

It appears some files have been lost.

All worked perfectly before (able to install from the ISO file) they
split and renamed to the two files "1" & "2".

Anyone see this problem before and know what's causing it.

Any advice would be appreciated.

Cheers,

Jim