Rebuild combinations

Have all sorts of problems with my site configuration. Been trying to get the product page to show exactly what I want and that is;

  1. Options with invantory tracking.
  2. Out of stock option hidden
  3. All stock showing to non logged in and only instock to logged in people
  4. Would also like the stock level to show next to each instock option.

    But I've been looking at the general setting and turning things on and off it see what happens but things like “Show out of stock products:” has no affect and I'm clearing the cache each time.

    After giving up on that I now find a category has some options but at least one shows no options in the update inventory section. So the only answer I really want not is what happens if I click “Rebuild combinations” ? I really think the server might blow up !