mMathab has been pulling out articles from the Google archives related to SW and here's a great one he's found on this subject:
http://news.google.com/newspapers?id=OacaAAAAIBAJ&sjid=DC8EAAAAIBAJ&pg=6425,8183100&dq=recover-12-copies-that&hl=en
(had started typing it in, so here's part fo the text. typos are mine)
The digital remastering will be finished next month after almost three years of work, at a cost of $30 million. The re-editing process has been laborious. The negatives were badly damaged after 20 years of wear and tear, and the Twenthieth Century Fox had to mount an international hunt to recover 12 copies that had never been returned from cinemas.
Luckily George Lucas found an unused "protection copy" in his basement, and editors at his California special effect laboratory - Industrial Light and Magic, which devised tricks for 'Jurassic Park' - cut and spliced this and some of the negatives to create a clean master version.
Four people were charged with finding every piece of unused original footage from 'Star Wars,' 'The Empire Strikes back' and 'Return of the Jedi'.