Not sure where you were copying to, but if a very large file and you
are trying to copy from an EXT3 to a FAT32 drive, for example, you
would get an error. In this case the large file could be copied to an
NTFS partition but not the FAT32.

I copied it from a cd to my ntfs partition. when i looked at the
file's size from ubuntu, it was different when i looked at it from
windows. So, i always use windows 2 copy .dat file (not good)

My I ask what type of .dat file are you trying to crack?

I tried to copy a film. (not pirating though...he5x..)

Well, i really want to kick of Windows out off my laptop..and so far,
my Hardy Heron runs fine..so pliz help me with this one

What were the EXACT numbers? A major difference?

Some OSes will report 1024, others round off to a thousand.