T-bird security certificates

I think you'll find that Thunderbird imports other people's certificates (if they are included with a signature) automatically into its certificate store, as opposed to Outlook, which puts them in the address book (it accomplishes the same thing, as far as functionality is concerned). You can look for them in the Certificates area: Tools | Options | Advanced | Certificates | View Certificates | Other People's.

Now that I think about it, it may be that Outlook automatically imports into the Windows certificate store, but allows you to associate a certificate with someone in the address book. I'd have to check. But the functionality is the same. Certificates are matched to the cert's subject, which is usually e-mail address; it wouldn't matter which entry in the address book they were associated with: if the e-mail (or other parts of the subject) differed, that certificate wouldn't be used. Likewise, if it was in the certificate store, it would automatically be searched out by subject and used, whether or not there was an entry in the address book.

If you sign a message to which you attach your vcard, the certificate should automagically get imported into whatever the recipient uses, and should be available to validate your signatures or encrypt for you. The only deficiency would be if your vcard gets detached from an e-mail message; I don't know about that.

At any rate, the folks at the Mozilla Thunderbird support forums would know for sure about both. All ThBP does is launch the ThB program, it doesn't change the way it handles certificates.

Everything rab040ma said, plus, you should consider updating to the newest release of Thunderbird Portable, 1.5.*.* is quite outdated.