OK, I have borrowed the original EMI CD, and it plays perfectly on my PC, using Windows Media Player. I can, however, recreate the effect you have described, by
only playing the right channel. As I suspected, the lead vocal is isolated to the left channel, so by playing the right channel only, you can get a near instrumental version.
What media player are you using? Somehow, it seems you are only hearing the right channel. To test this further, try playing something like the operatic section of Bohemian Rhapsody. If you know it well, you should immediately notice some parts missing, and if you don't know it, it will probably still sound weird and incomplete.
Something else you could look at is the speaker settings. Go into Control Panel > Sound, Speech and Audio Devices > Change the Speaker Settings, which should bring you to the speaker configuration window. Click the Advanced button, and from the drop down menu, check that one of the stereo settings is selected.
Let is know how you get on.