prankz, you are from the UK so you are very lucky. Here is a real experience from a lucky UK customer.
I submitted my RMA form on Monday morning. Just gave brief details of the problem and told them I wanted a new drive. In the afternoon Plextor Europe replied to my email and said the RMA has been authorised. They asked me to run PXInfo.exe and submit the results. I did. On Tuesday morning I got an email saying a new drive had been shipped and would leave Brussels in the evening. They even gave me a link to DHL website to track the shipment status. Wednesday morning DHL delivered the new drive at my door.
Plextor said the old drive might be required to be sent back to them and they would contact me within 2 weeks and said that if I didn't hear from them within 2 weeks then I should destroy the drive. I never heard from them again so I keep the old drive.
MarioGarcia, are you from the UK too? If not then the procedure might be different. For example, people in the US have to send the defective drive back to Plextor first and they have to pay for the shipping. But I don't think they are gonna let you RMA your drive. But you can try. No harm in trying. (suppose that you are from the UK).