Junk Files in windows/messaging folder

I have an HP Ipaq 114 which I sync with Outlook on a Vista PC. I have noticed that I have a large number of junk files in the folder windows/messaging. The names of these are all strange ie little squares, foreign letters and other various symbols. When I click on them it tells me they are system files. I am unable to delete them. I could leave them but whenever I use Spb backup to make a backup of my Ipaq it comes up with an error saying that these files could not be copied. Where have these files come from and how do I get rid of them?

Many thanks.