That's terrible. It would really suck if such a little oversight could mean that they are able to give you a zero.

Is it really that hard for them to check themselves which of the four test forms you've used ??

I would do as Mark suggests, but if that doesn't work I'd be VERY surprised if there wasn't a way to fight this. Check the exam rules. Good luck.
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Riocar 80gig S/N : 010101580 red
Riocar 80gig (010102106) - backup