simple way to securely destroy deleted files in a file system

["H.S." <hs.samix@gmail.com>]

I have a couple of hard disks in a computer which is to be recycled. I
want the windows OS in it to remain functional, but I want to be sure
that I have deleted all my personal files securely (never used the OS
that much anyway and there is hardly any important info in its registry
or browser). There are a number of documents that were deleted in
Windows the usual way (Shift+del) and I just want to make them
unrecoverable.

Its first and second partitions (sdc1 and sdc2) are vfat. I was thinking
of mounting these on /mnt/scd1 (and scd2) and then doing:
# dd if=/dev/zero > /mnt/sdc1/zeros.bin; rm -f /mnt/sdc1/zeros.bin

and the same for scd2. The idea is fill the partition with new data thus
overwriting any deleted files' data that is lying around. Would that be
adequate? The objective is just to prevent a casual recovery, reading
and copying of the data by a future user, so I don't need multiple
over-writes.

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