graham01 , it is definitely a 1GB memory chip. When memories are hacked, you can "store" files over the actual memory capacity. But anything over the 1GB point would only contain the filenames and not the data.
And if you played these files over the 1GB point, you'll experience player restarts or "format error" messages, sometimes your player firmware might be corrupted. Which might be one of the reasons your player is dead now.
The memory hack is meant to fool the Windows OS, so you will see just under 4GB (about 3.98GB) in My Computer.
But anyway, do you still recall your previous working firmware version? If not, you will need to try all the firmwares in the downloads section here
http://www.mympxplayer.org/actions-9...mare-dc37.html
There aren't many v9.0.xx firmwares as the firmware extraction tool current cannot support those above v9.0.43. But give these firmwares a try first.