problem with unknown player
 

Hello!
Recently i recieved one 4.3 inch touch screen player, which looks like this one:
4.3" Touch Screen MP3/MP4/AVI/RM/RMVB Portable Media Player (4GB/480x272px/TF Slot) - Free Shipping - DealExtreme
I don't know where is purchased from, because it was a gift.So i don't know what's the manufacturer.
In the system information shows :
Manufacturer : RockChip
Product Name : RK261X SDK
Major Version ID : 1.3.5
BUT it seems that's not correct info, because in Device manager it shows that the device is RK28xx.
I also unlocked the hidden partitions and tryed to make some changes in the firmware,but without
success...
I tryed to flash it with all possible programs form rk26 to rk 28..no success...
In the hidden partition there are some difference in the files...there's no sense...boot file is RKCrownBoot,but the other one is RK28IMG.CHK.
So can you tell me, Please how to change thee firmware? And is it possible to change it?
Because it seems that it's locked somehow.When i overwrite the files and restart the player it loads the old firmware.When connect it to the pc - in the hidden partition there's no other files except these of the firmware.
I'll be very grateful if somebody guide me how to change the firmware and solve this problem.
Thank You!