Duplicated emails

Hi,
Probably not the right forum, but someone may be able to help me.
It seems that whenever I send emails - to yourselves, eBay or others - the message gets duplicated: this has caused duplicated orders on eBay, which took effort to sort out.
Whilst not strictly BB related, I wonder if anyone else has experienced anything similar, and how did they rectify it.
I run:-
o2 BB on LLU, and very satisfied with it, thank you very much Bob (RobertoS)
XP - SP2 installed
4gig memory
3gig Dual-Core Intel processor
ESET antivirus

I use;-
Outlook Express - Windows Live Mail
Firefox (latest)

I regularly use Malwarebytes/Superantivirus/CCleaner and Glary Utilities

I use COMBOFIX on occasion.

Any help much appreciated.
Cheers, Les.

In reply to a post by lelboy:

..... Outlook Express - Windows Live Mail.....

Why two clients that are basically the same? This could well be your problem.