After download file FLV in website youtube, i can’t play that file in Microsoft Media Player. I use Microsoft Vista Home Edition. Than, search in internet (google), I find opensource FLV Splitter, this is Decoder for FLV in Media Player.
Open Source FLV Splitter is an excellent piece of software if you need to be able to use Windows Media Player for FLV.
Download Gabest Flash Video Splitter for Windows XP/2000/2003 from:
Download Gabest Flash Video Splitter for Windows 95/98/ME from:
To install the FLV Splitter is simple. Run the executable file that you downloaded, click Install and then click Close. Now to test it out, try to open your FLV files with Windows Media Player. Right click the FLV file, choose “Open With” and then select the “Select Program” option. From the list that pops up, select Windows Media Player. If the splitter is installed and FFDShow configured correctly, the file should play back without a hitch. If you get a message alerting you that the extension is not recognized by Windows Media Player, select “Don’t ask me again” and click Yes. (http://www.afterdawn.com/guides/archive/how_to_play_flv_files.cfm)