Thanks for the replies, but whatever the problem is it lies within the way the disk is being read by XP.
I have looked under 'my computer' properties and Nero 5.5 and both tell me that a 650 mb CD-RW containing around 600 mb of jpegs is full and has a total capacity of only 4.25 mb!
The only way I can resolve this is to wipe the disk and replace all data, which being an RW is done at 4x and takes forever.
I see the same properties for the disk regardless of whether it is in the CD writer or the DVD drive.
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