It's not loading the files, but the computer shows it

The best way to figure it out is take a very small file, like a video sample and then convert it into a bunch of different formats there are basically 100's of different "types" of video files. Within .AVI you can encode it a 100 different ways of AVI. so you should run through and test which ones will work. I can be pretty sure it will be a pretty small resolution that will work. 320x something or to that effect.
Thanks,
Lee

- Connect your MP3 player to your PC/Laptop and use 'Windows Explorer' to locate the drive for your MP3 player. - Right click on the mouse while pointer is on your seleted MP3 drive and select 'properties' - This will show your actual 'Used space' and 'Free space' for your MP3 player. - If you are using more space than you thought, double click on your MP3 drive to display your files in 'details' mode which will show the 'missing' individual file size details that were previously loaded. . Hope it helps!

try opening the device from My Computer and dragging the files to your pc

Format the player and use Windows Media Player 10 or higher to sync the player.

http://www.sansaworldmp3.com/
http://www.sansaworld.com/

down load vlc media player (video lan client ) it plays anything you can thinkof ask.com it

 “I can’t load any more songs into my mp3 player” or “An incorrect number of songs show up.” (MEMORY/FORMATTING ISSUE)
Sometimes, you can’t load any more songs into your player because, well, there just isn’t any more space left on your player.  Mp3 player product documentation does not actually list the actual amount of memory that you can use in your player, and it doesn’t list the actual number of songs that you can realistically fit on your player.  Every mp3 player needs a certain amount of memory space to operate and firmware upgrades decrease this available space – so, your 2GB mp3 player actually contains only 1.7 or 1.8 GB for music and other media files.  The mp3 player that says “can hold up to 1000 songs” may only hold 400 songs – the product documentation assumes that you are loading a 1-minute song in the lowest possible quality format – not very realistic.  A single 30-minute audiobook, speaker file, or video can seriously bring this number down.
Other times, however, you are experiencing a formatting issue or memory corruption.  If you plug your mp3 player into a computer that has an NTFS file system, and then plug it into a computer that has a FAT32 file system, you may experience this formatting issue (file system/formatting issue).  Similarly, this will happen if you plug an mp3 player into a computer running Windows Vista, and then plug it into a computer running Windows XP (operating system/formatting issue).  Or, if you plug your computer into a PC, and then into a MAC (PC or system/formatting issue).  Or, if you plug it into a computer with Windows Media Player 10, and then into a computer running Windows Media Player 11 (software/formatting issue).
Apparently, if you add too many folders, especially via Playlist, via Windows Media Player, the Mp3 player's file system will become unstable - it can only handle a certain number of additional folders. To resolve the issue:
1. Connect the player to the PC using the USB cable.
2. Open Windows Media Player.
3. Go to the Sync or Devices tab and delete all content from the player.
4. Go to the Tools menu and select Options.
5. Select the Devices tab, highlight the ILO or Siren player and click on Properties.
6. Uncheck the box "Create Folder Hierarchy on Device"
Now, when music is transferred, it will be placed in the root directory of the flash memory disregarding the folder structure and allowing all tracks to be seen.

This procedure was designed for Siren Mp3 players, but is applicable to many other Mp3 players. It is not a guaranteed fix for every Mp3 player and every error of this type, but it is certainly not a widely known or reported solution.

Before proceeding with a format or reformat of your mp3 player, check with the manufacturer first.  On many players, a format or reformat along the lines suggested here will override your mp3 player’s native formatting and render your player unusable.  Transcend’s T.Sonic player is especially susceptible to this problem, and should never be formatted.  Also, the instructions below are for Windows-based PCs, not for Macintosh.  There are two ways to format an Mp3 player - one on the computer itself, and one in Windows Media Player. Both methods will end up erasing all the songs on the player, but the player will be "good as new" after that. Sometimes reformatting in this manner will override the player's native formatting and cause problems - this can be reversed in some cases by updating the player's firmware or reloading the firmware. Firmware upgrades are available from most manufacturers' websites.
WARNING: The following procedures will erase all songs on the player.
Check if the file system is NTFS. If yes, format it to FAT or FAT32. - Connect player to computer, double-click my computer, right click on icon of mp3 player and select format. This only applies to Windows-based computers.
You can also format the player in Windows Media Player itself:
Connect your Mp3 player to the computer and open Windows Media Player. Click on the Sync tab. Pull down the drop down menu underneath the Sync tab by moving your cursor over the Sync tab and left clicking on the little black arrow underneath the Sync tab. Highlight "name of Mp3 player here 1GB" (wording may vary slightly), and then select "Format." - this should erase everything.
-Tha Mp3 Doctor

the best way for that is to read your manual.

MINIMUM SYSTEM REQUIREMENTS
Windows XP SP1
Windows Media Player 10
Intel Pentium class PC or higher
CD-ROM drive
USB 2.0 port required for hi-speed transfer
CONNECTING AND TRANSFERRING
Connect to your Computer
1. Connect the small USB Cable Connector to the USB port on your computer, and then plug the larger
Cable Dock Connector in to your Sansa c200 port.
2. Once connected to computer, it should be detected by the operating system automatically and is
shown as an additional drive called “Sansa c200”.
SANSA MEDIA CONVERTER
You will need to use Sansa Media Converter to transfer photos to your Sansa c200. Insert your SanDisk
CD and select Sansa Media Converter to install it to your PC. Then you can load your personal photos
onto your Sansa c200 by using Sansa Media Converter.

TRANSFER MUSIC
To transfer music to your Sansa c200:
1. Connect Sansa c200 to the computer.
2. Drag and drop files from your computer to Sansa c200 by using a variety of music software
programs to transfer/synchronize your files.
3. In MTP mode as long as the files are WMA or MP3, they can be dragged into the Media folder.
Otherwise, they can be dragged into the Data folder (these files will not appear on the player).
4. In MSC mode, files/folders can be dragged/copied to the device.

Can't create directories directly on the m250. I've got about 1000 songs loaded (already broken into subdirectories) that take up 800 MB and the device claims that it's full. (Firmware is also updated to 4.1.08A)

Same thing happened to me. I was using windows media player to sync my song and it says my player was using 260 mb of space even though it was formatted time after time. I simply loaded as many song as I could fit on the player. When I unplugged it and plugged it back in, windows media now showed that missing 260 mb of space as available. The only catch is that the song I had already uploaded on to the player were not shown on the sync list.

Ok I have same player, same problem. Turns out Windows Media player copied the files into the FM subfolder on the device. FIX: connect device to computer. Do not open WIndows media player, instead open windows explorer, in there you should see the ilo as a new drive. Click the drive and go into the FM folder, now select all files and drag them directly to the drive. The secret is the files have to be outside of the FM folder loose in the device (not in any folder) After that I safley removed the device from the system tray icon and powered it on and the songs were all there. It runs an index process that creates the lists, this takes a second.