I guarantee you it has hacked memory. Every player from Hong Kong/China on Ebay listed with 8GB plus is hacked. I have bought literally over a 100 of them and every single one of them bar a few 4GB players and the 2GB players are hacked memory.
You can use Check Disk to remove the hack quite easily. Forget about modding them too as you will likely brick the thing.
I have bricked my fair share.
If you have not left feedback yet and you have only just purchased it then demand 50% partial refund and you'll find yourself with a 1GB or 2GB player for $10. Not a bad deal imo.