[snakes1100]

Hmmm, a easy way as i do this sometimes to replace code, i use Edit+, you could take a backup of your forum via a sql file and edit it in Edit+, use the replace function Edit+ has to search out the link and replace the part you want edited.

Ie:
Find what box = http://subdomain.domain.co.uk/audio
Replace with box = http://www.newdomain.co.uk/sound

As it simply replaces the text every time you click find next, it shoudlnt take you that long to do, then simply import the backup sql file.