I give up code signing.

[NewsArchive]

I haven't had to do it myself (because I'm a girl and actually read the
directions and do it right the first time! <G>) but a quick Google of
"export code-signing certificate" turns up a number of hits.
Here's one: http://www.tech-pro.net/export-to-pfx.html

Even if you had specified "in a file", BTW, you'd still have needed to use
the same machine to collect it, as mentioned in this PDF:
http://www.beachbunnysoftware.com/webinar/CodeSign.pdf

HTH

Jane Fleming