Converting the disk format will wipe the data currently on the disk though.
Many devices do not like NTFS - I think its mainly because most TVs,media players have linux kernels and Microsoft (which 'owns' the NTFS format) make it a bit hard for outsiders to access the specifications.
Assuming you can re populate your MyBook (ie you have everything backed up somewhere else), you can do this to make it FAT32:
Thats for windows - I gather if you look on the WD site they have a tool you can download that will do it for you. NTFS is a bit more efficient for file storage - but you probably would notice much real difference. The one possible gotcha is the I think the maximum file size is 4GB in FAT32. So if you had any individual files larger than that you would have to split them.
I see that apparently you can convert from FAT32 to NTFS without destroying the data on the disk but cant go the other way - so have a read up first.
I found a few more people on google with different model sammies asking similar questions to yours - ie Drives that would/wouldnt work and the FAT v NTFS issue - so would think this is quite possibly your problem.
Also - on re-reading the posts above - if the TV can access files directly on a USB device then thats one way of accessing the files. If the TV supports DLNA (it will) then you need to have software of some type 'pushing' the file (streaming?) to the TV. So hence the reference to twonky (and there are other programs). I think you just want to plug in your USB drive and playback the files dont you?