Hi there!
Was desperately looking for a programme that allowed me to convert my Sony Ericsson vCard (Whole Address Book) to a format that would allow it to be imported easily into a PIM. Nothing really worked (tried the lot - Open Contacts, EPIM, etc.) and then came across this freeware programme:
http://www.processtext.com/abcvcard.html
Download the file and Uniextract to a folder of your choice. The programme loads from abcvcard.exe in the MAIRDIR folder.
Sorry - testing whether it affects my registry and is therefore portable according to your rules (which seem perfectly reasonable) is beyond my technical competence But the programme works and converts vCard into around 20 different formats.
Hope this is useful for someone else...
Thanks Andrew for this great site