Flac is an audio codec used for preserving audio format and compressing them without any quality degradation. Often, you can convert Flac into mp3 format using freeware software or manual methods. But if you want to directly play Flac file onto your Windows Winamp media player then get make use of winamp plugins.
And if you are using the latest Winamp player version then you can right click on the flac file and open it up with Winamp program as it comes with pre-installed support to play flac files or else get the flac plugin for other older winamp versions you are using on your windows system.
This is the easiest and recommended way to play Flac files in Winamp. You can also make use of other media player to open and play flac file extension. Some of the well known windows player that can play Flac files without the need to download any add-ons or plugins are :