questions concerning BC v0.7

I have upgraded my BC 0.56 to v0.7, but have some new questions about BC v0.7:

  1. Should I allocate disk space before downloading?

  2. Where can I set my default browser in BC?

  3. I double clicked another .bitorrent file while BC was downloading files, but then my Windows freezed.

Was this a bug?

Please help if you could!