After hours of trial & error I figured out the issue for mine, i came across your post & if you still check on here I hope this helps you.
1. Use WinFF to convert your files (it takes some time to do so). If you need to DL it just google it.
2. You want to select the conversion type to Xvid for PSP either 4:3 or 16: will work
3. Just drag & drop the converted file into your video folder & then go to your videos & it should work.
Hope that helps you out, if not enough detail just post again & I'll try to give more instruction.
After several weeks of trying, I FINALLY got a video converter to work for me so I can convert video files to mpeg4 to play on my Walkman, and now the Walkman won't let me transfer the files. I get this error message:
The <name of file> file type is not supported on this device. If it is a media file, you may be able to use Windows Media Player to convert the file to a playable type prior to transfer. Do you wish to skip this file now?
The only choices it gives me are Skip, Skip All, and Cancel and it won't allow me to transfer the file to the device. I don't think it's a problem with the file because I tried to transfer a video that I KNOW the device will play because it's played it before, and I still get the same error message. I read that it was something to do with Windows reading it as an MTP device, but there's got to be some way to get around it or at least get Windows to just see it as a USB Mass Storage device. Please help me!

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