The seller has sent me a message saying 'send it back and i will either give you a replacement or a refund'. But i am not sure if i should because he might keep the mp4 player and not give me a new one. What should i do?

can anyone tell me how to claim money from a seller?
this seller is getting on my nerves, he says there is something wrong with his paypal

Don't send the player back at YOUR cost! The seller will keep the player and the money and you will never hear from him again. If I were you, I would tell him that. Also, tell him that you are familiar with memory hacks and know that he intentionally scammed you and you're not giving him more money. Let him know that you KNOW what he's doing. Worst case scenario is that Paypal will close the claim and you are out the money. Which is better than if you sent it back and were out twice as much money.

I have told him that i know about the memory hack and that he has scammed me. I said to him that i will be willing to give him £4.00 more if he gives me another 2GB MP4 player to make up 4GB. His answer was no. He also said that his paypal account doesnt work for some reason, i think he is lying. Then i sent him a message saying that i would leave him bad feedback and that he scammed me and i would put a claim to paypal. I am new to paypal, i was just wondering if someone would tell me how to claim money from a seller, would i get all the money back i gave?
Would i have to send the player back to him?

Obzdadon , firstly i don't recommend sending back the player at your own cost to get a refund of the purchase price only. You would have lost some money and got nothing in the end.

What method did you use to fund the purchase via paypal? Was it credit card? If so, contact your credit card company to do a chargeback.

If you can convince your credit card company that it is a fraud, and it makes no sense to send the player back at your own cost when the seller sold you a hacked player in the first place, they might likely do the chargeback.

Paypal can't do sh*t about chargebacks, and very likely you should be able to get all your money back.

The seller Said he will give 'partial refund'. He hasnt told me how much yet