Thank you for both replies. It was much, much easier than I thought. Just cleared the disk via Disk Utility from my Mac OS X disk. Popped in my 4.6 CD and done a usual install. Worked perfectly! startx worked perfectly first time too!
Thank you OpenBSD team/users! P.S: In my 4.6 CD booklet it says: cd /cdrom/4.6 /packages/<arch> I think you've mistakenly added a space after the 4.6. Or am I missing something? John