Problems with Comodo with XP/Win7 on Outlook 2003/2007

I am using Comodo Secure Email v (32 bit version) on a Windows XP and also tested on Windows 7 32 bit OS with Outlook 2007 as my email program. I have certificates for one of my email accounts. I have CSE set at the medium security level.

We want to purchase an enterprise license but when i explored this product i am unable to run this free versio. The certificates on both pc’s / accounts are displaying fine and installed at appropriate location but when i try to send an email then they do not encrypt message using those certificates.

What to do? Any thoughts? Please help.