Yeah i know, you need avisynth + directshow and virtualdub (if you want to encode in .avi (divx,x264 etc...) or maybe tmpgenc (for mpeg2 dvd/svcd) that's the best way & i mean the BEST to convert all the exotic videos you find on the net (.wmv, .mov, .flv, .mp4 etc) not to mention avi's & mpegs
Anyway, once you get them just open your notepad an copy/paste this line & save as .avs (not .txt) pick type = all types before:
DirectShowSource("C:\Documents and Settings\blabla\Myvideo.flv",FPS=29.970, ConvertFPS=true)
explanation:
first, you write the path of your video
second you stipulate what's the frame rate of the video (it could be 24.000; 25.000; 23.976 but here i keep it simple it's 29.970 a.k.a standard ntsc
Then you open this script with virtualdub or tempgenc or another software the which must accept .avs scripts.
I suggest you get the k-lite codec pack to begin with
http://www.codecguide.com/
Peace