Download Adobe Media Player.
I already tried that, but from the website:
Effective September 16, 2010, Adobe® Media Player software will no longer be available for download from the Adobe TV website. Effective December 15, 2010, Adobe Media Player will no longer be available for download from Adobe.com.
Oh. I wasn't aware of that.
Adobe Media Player is installed with practically every Adobe software install I have made in the last 3 years. If you have the installation disc for, say, PhotoShop or Flash or Flash Builder, you probably have Adobe Media player installer too.
I did a quick search and there seems to be a zillion sites offering methods and tools for playing flv - http://www.bing.com/search?q=howtoplayflvfile