... but comodo does not see any large file more then 3-4 gb
... copying a large volume like 3-4 GB, it used to abort halfway. <- I have this situation.
Are the files that you can't backup larger than 4 GB or smaller than 4GB?
Can you successfully backup files below 3GB?
What format is your hard disk - NTFS or FAT32?
Ewen :-)