It's hard to know if you did it correctly if you don't post the exact code you used and then let us see the results.

It was:

ORDER BY parentid, title

Can i sort sub forum by lastest thread/post reply?

Anyone that's still looking for this, follow Lynne's instructions, but use this:

Now what will happen is the display order will work normally. But if you want some subforums to be listed/displayed alphabetically, just give them the same display number. For your existing forums to get this, just go to maintencance and rebuild forum information. All new forums added will get placed alphabetically right from the start IF you use the same display number. If you use a different number, it'll will be listed where it normally would. But if you later decide to change the number to the same as the rest and hit save, it'll pop right in line with the alphabetical stuff. So far I haven't seen any issues with this method and it's incredibly simple and easy to manage my 400+ subforums. Some are alpha, some are not, and it doesn't take me ANY time to mess around with display order numbers.:D

*EDIT* A little clarification. Just because some items have the same number, doesn't mean they will be sorted alphabetically. They have to have the same number AND be subforums of the SAME forum or category.

big Thanks to zhono and lynne . this helped me and safed a lot of work!