As aliasbody wrote, you can shrink an NTFS filesystem to create free space on
the disk where you create a new partition with XFS as a filesystem. As a
consequence, if the "fill-rate" of your NTFS is below 50% (a bit more
actually because I guess XFS has a larger overhead, i.e., needs to write more
meta-data) or if you can remove some files to go below 50%, then your problem
can be solved with no additional copy (you will need to defragment the NTFS
filesystem so that all data are grouped in the same region of the disk
though). Once the data copied to the XFS partition (since GNU/Linux can read
NTFS partitions, it is trivial and can even be done with a graphical file
browser), you can erase the partition with NTFS and grow the partition with
XFS.
By the way, XFS partition cannot be shrunk. This probably the worst drawback
of XFS.
Notice that, if you can, it is always safer to copy the (crucial) data
elsewhere. Have you thought of DVDs? It will take ages but it is a solution.
I recommend you to manipulate partitions from a Live medium such as a
Trisquel Live CD/USB key. In this way the hard disk is not solicited by the
system. As aliasbody rote, GParted (included on Trisquel's ISOs) is a
user-friendly interface to do such manipulations.
As for file sizes, 5 MB *is* large. By small files, we means files up to tens
of kB.
