To change the size of an existing partition on hard disk
here is a free software called QtPartED.
available free as a bootable CD from:
http://www.sysresccd.orgto use it down load the CD ISO image, burn it to a CD-R
boot from the cd at the prompt just type:
run_qtparted
and press enter on the keyboard.
enter mouse number (PS/2 is 3)
and you get a partition Magic in GUI (graphical user interface) in linux.
it is exactley like partition magic in DOS;and supports all file systems
including NTFS,FAT,FAT32,EXT3.
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this tool is also available on KNOPPIX the Live Linux Boot CD
use the Menu (system tools)
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I think this second time you had the correct MBR on the new HDD already.
I would hang on to that ISO in case you change your Hard disk again.
regards ben