According to JiYeon's English Wikipedia page, she appeared in this music video: (if anyone knows where I can get a high quality version of this, please let me know)
I had a look and discovered that Shin Bong Sun was in it too.
Considering how JiYeon appeared in the MV for only a few seconds (less the singing time allocated to Some-Non-Singing-D members of other popular girl groups), I wonder how one even manage to discover that JiYeon is in the MV. I've scanned through the Korean wiki page for JiYeon and there's no mention of this at all; and I don't think a normal T-ara fan would watch such old MVs if not for JiYeon.
Anyway, if you've not click the video, go ahead and click it, I've saved your trouble of watching the whole thing by setting the start time to where JiYeon appear. Other visible times are 1:31, 2:34, 2:48.