If it's short (under two minutes) the free version of Visual Hub works very nicely. For longer videos, you'll need to register it.
I use Super C - converts to and from tonnes of audio and video formats. No use if you just want to go from wmv to flv, or vice versa, but if you want to choose from a long list of many formats (iPod, PSP, NDS, flv, avi, DVD) super C is a handy tool, though can put a bit of a drain on the system.
For converting my flv to any video format I use Flash to Video Encoder PRO. It normal creates my flash files with good quality. You can try it too.
it is freez which is by small video soft.download from here : http://www.smallvideosoft.com/download.php
SUPER is FREE, it converts pratically ALL filetypes to all filetypes it is amazing, in my opinion anyways, i always use it, very very good especially for free!!