stefanyb , for a start, perform a format on your player first. This will verify the actual memory capacity and determine whether your player had been hacked or not. Guide here
http://www.mympxplayer.org/how-to-re...ck-vt2400.html
Next, you can theme your player. To do so, you need to extract your current firmware and repair it. Guide here
http://www.mympxplayer.org/how-to-ex...tool-vt66.html
Then modify it using the S1res tool. Guide here
http://www.mympxplayer.org/how-to-mo...ool-vt206.html
After that, save the new firmware, and flash back into your player. Guide here
http://www.mympxplayer.org/how-to-up...ayer-vt46.html
There are many themes to try in the downloads section. But not all will be compatible with your player though.
Do not use a themed firmware, but rather use your own firmware and swap the images. Or you'll risk killing your player.
Just drop more questions in the forum if you need more help.