the ipod ONLY play mpeg4 with h264 encoding, if you have the file in Quicktime or (only on systems with windows media components for Quicktime installed [ Microsoft website for this one]) WMV you can import it into itunes then form the itunes advanced menu use 'convert for ipod' and then the converted file will be mpeg4/h264.
getting this from a DVD or other format needs you to get a convertor or RIPPER and you can get these via www.versiontracker.com
although many shareware will either overall a trial logo or limit it to 30 seconds until you pay the unlocking fee.
for the Mac I use handbrake to RIP DVD's and it does correct to MPEG4.
the reason ipods only use mpeg4 is that its the only OPEN format that does not need an extra codec loading it into the operating system.
WMv, RAM, AVI, etc are not open formats they need codecs adding to the system to play and often these are locked to one program to play them.
ALSO You need to tell your ipod to sync apps, Music (or Movies etc) as by default most syncing is OFF other than Music which is ALL unless its too big for the ipod/iPhone when its none.
Plug ipod into itunes.
click on the ipods Icon its summary page appears.
click on the tab that says Video
click on 'Sync All' or ' Sync only selected'
click on APPPLY BOX
click on SYNC box.
voila it now will sync Video