Ha, I should have checked here first
I've spent ages changing all the files from bac to dbx. There where a few files there that didn't seem to do anything but I've kept them there just in case they're system files of some sort.
The good news is that I've deleted all the crap files and replaced these with the good ones. All seems to be working at the mo and I've set up a "backup" folder on my D drive to keep my copied folders in.
So what do you guys think I did? Or is it a glitch of Outlook? I did have conection problems with my email client yesterday, could it have been that? I'd like to find out to prevent this happening again.