Songs not uploading
 

I bought an s1 mp3 player that has a screen so it's not the really small ones. It has 2 gigs of memory and I added about 50 songs at first but only the first 40 would play and whenever i got to the others the player would restart, so i deleted the other songs and all the other songs left on played fine and then i deleted a few others and added a couple more and the new ones wouldn't play either. So now only about 23 are playing and if i add any others through windows media player they won't even show up and if i add any through windows usb thingy then when i try to access them the player restarts. Is there any special way i'm suppossed to add songs or any tool i could use?

EDIT* I have discovered that the reason my mp3 player is doing this is because it only has 256 megs of memory. Unfortunately it was hacked, is there someplace where i could buy like a gig or 2 gig memory chip and install it myself?