Hi Alegator, I see you got a bluetooth adapter then?
That's not true, Zaher - Provided that the pairing devices both use the same profile (ie. in this instance 'headset') then they should communicate nicely. I know there are some devices which don't get along so well, but as for why I do not possess that knowledge.
Here's a handy tutorial by
Wei-Meng Lee that I came across recently.
So to answer your question, I don't think you should have too much trouble finding a headset that you can use both for your PC and mobile. You won''t need to buy separate devices for each.