Hi Neil,
If the item has been opened then I'm afraid a 20% restocking fee will apply, but if it is still sealed then there will be no charge.
I believe the drive you are looking for is something like this:
http://shop.cd-writer.com/catalog/liteon-8x-int-slimline-black-bare-sata-p-103499.html
If you wish, we can arrange to raise a credit note on the drive you are returning, and use that as partial payment towards the Lite-On drive (if its what you're looking for).
I will send you an RMA form now. Please complete it and I'll authorise your drive for return.
kind Regards,
David