The cheapest way to fix the problem is to get a longer BB (sounds like you need normal square taper), as outlined above.
If you're getting a new square taper crankset because you want to, fit it on your existing BB, measure the chainline, and then get a new square taper BB to fix the chainline. I don't think that a BB to fit Stronglight 2000's will be specific.
If you are going GXP or Octalink, then you need to know what your hub chainline is from the centre.
The cheapest way to fix the problem is to get a longer BB (sounds like you need normal square taper), as outlined above.
If you're getting a new square taper crankset because you want to, fit it on your existing BB, measure the chainline, and then get a new square taper BB to fix the chainline. I don't think that a BB to fit Stronglight 2000's will be specific.
If you are going GXP or Octalink, then you need to know what your hub chainline is from the centre.