Sooz, I don't have a phpBB board, but most message board are similar. On the Topics page, there should be little boxes next to each thread that you can check. Then scroll down the page to the bottom and look for a drop-down menu box. One of those options would be "Move Threads".

If there are a lot, go into your ACP > Forums > drill down to the forum in question > edit

Scroll down to "Topics per page" and change the number there to anything up to 127, scroll down and "submit".

Next, visit the forum in question and hit the MCP button/link. On your board, this is labelled "Tools". There you will find all topics listed with checkboxes to the right.

Hit the last page (pager at bottom) and then use the "Mark all" link (just above the pager) to select all your oldest topics.

Select your action (Move) and press "Submit".

The next page is a confirmation page, where you choose which forum you are moving the topics to. On this page, you will want to UNcheck "Leave shadow topic in place" before submitting.

The niggle here is that once complete, you will be returned to page ONE and not the last page, therefore you need to page to the last one again. This is still quicker than using the sort process because the sort order is reset after you submit too! Just repeat the previous paragraphs until you get there.

Once complete, return to your forum management, reset the "Topics per page" (default "0") and submit.

Enter the forum in question. Enter the MCP by using your "Tools" button. Scroll to the bottom of the page so you can select the page they are on. Against each individual moved topic you will see a link: "Delete shadow topic".

Tip: Middle-click the link.

On the following page, confirm "Yes".

(You can then close that page and work up/down your list on the previous page. This is much quicker than doing the full cycle every time.)

You're welcome.

It won't take you long once you get in the habit of it.