How to clone Windows XP back to your HD?

Long, sad story made short.

I have a Samsung Netbook running Windows XP Home, SP3.

I set it up to dual boot with Ubuntu, just so I could play around with
Ubuntu.

Well, Ubuntu started giving me trouble: my internet connection went
south,
I was unable to adjust the brightness of the Netbook screen, etc., and
when
I looked for troubleshooting help on the internet, it was all Greek to
me as
it involved working with Terminal.

I did a search for removing a partition in Windows XP and found "How
to use
Disk Management to configure basic disks in Windows XP" on the
Microsoft and
followed the instructions there.

Now, when I try to boot the Netbook, I get this:
GRUB loading.
error: no such partition
grub rescue

When I research what this means, the solutions, all on Linux sites are
baffling.

So...

I cloned my Netbook HD about a month ago to an external HD.

How would I go about erasing the HD of the Netbook and cloning back to
the Netbook HD the
operating system from the external HD? Is this possible?

Remember, Netbooks do not come with an optical drive.

Many thanks.