Need to remove a corrupt data file from my Nandroid backup

[JohnnyACE562]

Tried to flash a Gingerbread ROM, didn't work, and now when I try to flash back to my only saved backup, ClockworkMod always freezes up during the restore process on the same PNG file.

How do I access my backup to get rid of this file? What program should I use? Please help as soon as possible. I DON'T want to start Angry Birds from scratch all over again.

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