you can format the device, maybe if you delete files on the device from the computer , you cause inconsistence between them, i suggest to erase files using the buttons on the device. about the high speed check the codecs in your computer,
I can’t play a file that Windows Media Player supports. What should I do?Most
likely, a required codec isn't installed on your computer. Typically,
Windows Media Player automatically downloads any required codecs from
the Internet and installs them. However, this may not happen for the
The necessary codec (typically, a non-Microsoft codec) isn't available on the codec server.
You have an older version of the Player and your automatic codec-download option isn't enabled.
The Internet security settings for your browser are set too high.
You're not connected to the Internet.
you have an older version of the Player (prior to Windows Media Player
9 Series), you can check your codec download setting by doing the
In Windows Media Player, on the Tools
menu, click Options
, and then click the Player
In the Auto upgrade
area, make sure Enable automatic codec download
is checked, and specify how often you want the Player to check for updates.
can change your Internet security settings (if you are logged on as an
administrator or a member of the Administrators group) by doing the
In Control Panel, open Internet Options.
Click the Security
tab, and then click Internet
In the Security level for this zone
area, click Default Level
If you can’t play the file after completing this procedure, restart your computer, and then try to play the file again.
you still can’t play the file, try to play another file with the same
file name extension. If you can play this file, then there is a problem
with the file that you want to play. For more troubleshooting
information, see the Windows Media Player Multimedia File Formats Web