Once you move your data to the new disk, boot it to make sure everything is o.k.
When happy, just delete the old partition(s), and use gparted to resize the NTFS to use the (now) free space.
If Mandy doesn't have gparted, download the liveCD - only about 50-60 Meg.
Might be safer to use anyway, and it's handy to have around.
Easy ...