Why is my PSP not showing the videos that i have saved in the file?

i have downloaded 3 videos from Youtube to my computer, then i saved it on the MP_ROOT file and in the 100MNV01 file. when I go to the video on my PSP, it says 100MNV01- 0 videos. i dont know what i am doing wrong, could someone please help me?
hi, I think first u should need a psp video converter to transfer them and then u can enjoy them on your psp. Aiseesoft PSP Movie Converter can convert any video and audio formats to MP4, H.264, PS3 MP4, PSP Video formats.
U can free download here:

DVD ripper is a computer program that facilitates copying the content of a DVD to a hard disk drive.

DVD Ripper can rip DVD to AVI MPEG WMV DivX H.264/MPEG-4 AVC MP4 MP3 WMA excellently.

pavtube is one of the best dvd rippers, It is versatile application and users can use it either to backup DVD to hard disk or to convert DVD movies to AVI, WMV, MPG, MP4, MOV, and 3GP, AAC, MP3, W4A, WMA, WAV and AC3 etc.

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The following steps guide u :
Step 1: Select and click “PSP Movie Converter”.
Step 2: Click “Add File” button to add your movie.
Step 3: Select the output video format you want from the “Profile” drop-down list.
Step 4: Click “Start” button to start your conversion and in a short while it will be finished.

Some powerful functions such as “Merge”, “Trim”, “Effect”, “Snapshot” are all available.

So now hurry up to have a try, I really hope u can enjoy your favorite video on your psp as soon as possible.good luck to u.