Your provided info does not give enough information to perform a diagnostic test.
But you can try this...
I/O error probably it's either the connetion between your PC and Player are not communicating properly or your MP3
internal media already has some defects.
With the player plug in, Go to My Computer. Right click on your player and click
on Properties. Inside the properties page, you should see a pie like chart. Blue represents used space. Pink represents
free space. If it's all blue, then there is something wrong.
If it's all pink then you have no data in your player. Do not format your player yet!!!!
Go to the Computer Management console and click Disk Management. It's located in the Administrative Tools (located
in Control Panel). Verify if there is a file system. It's Mostly FAT32.
Please post a pic from the Computer management console. This will help a lot.
If it's the Memory Stick Media you are talking about. If you have a card reader plug it in to see if it
works.
If you have unplug and plug in a external device without safely removing it. It will result in disk corruption and data
loss.