[vinzphua]

Here's a less then ideal solution:

Create 2 forums. Say Forum A and Forum B. In their settings:
Act as Forum: No
Forum is Active: No
Forum is Open: Yes

Now create the sub-forums in them.

Create another 2 forums, Link to Forum A and Link to Forum B. Their settings:
Forum Link: URLs to the Forum A and Forum B respectively.
Act as Forum: No
Forum is Active: Yes

Another variation, assuming your main forum A is already active, is to create Forum B as above. then you need to provide a link somewhere to Forum B.

The cons are:
- Forum B will NOT display like the main forum index page... i.e. things like Who's Online will not show.
- You can't separate searching of Forum A from Forum B without some specialised search page or modifying the current one.

There is a setting to force Forum B to use a certain style.