No audio on playback

I’m using 2.0.3,but have used earlier versions successfully in Win XP. I recently upgraded (?) to Win 7, and use Audacity primarily for vocal removal. I find that on a lot of recordings, even though I convert to Mp3, I have no audio at all, either on playback or if I save the file, no audio when i try to play that file. This is not every case, but mainly on older recordings, although it happens on newer recordings also. What am I doing wrong ?

Vocal removal works by “cancelling out” sounds that are in the middle of the stereo field (sounds that are identical in both left and right channels). It does not work with mono recordings (even if the mono recording has been “converted” to stereo, because the left and right channels are identical, so all the sound will be removed.
More information about vocal removal here:

Thanks Steve. i suspected that may be the case, but appreciate you’re confirmation.