Don’t toss any “bad” discs. You may be able to painlessly recover your data with a program that repeatedly reads sectors until it recovers them into an ISO-format file, to re-burn on the same type disc (CD or DVD of the same capacity) …
VideoHelp - IsoPuzzle 1.7 writes:
IsoPuzzle is CD/DVD recovery software. The goal of this program is to recover as much as possible data of damaged, bad burned or scratched CDs or DVDs. This version is experimental and supports only data CDs and DVDs with sectorsize of 2048 byte - Audio CD, VCD and SVCD are not supported. Requires ASPI.dll.
The program requires wnaspi32.dll and the Nero link is bad. It can be found at: ftp://ftp6.nero.com/wnaspi32.dll. Works as advertised, though it grinds to a crawl (about 1 KB/sec!) on bad errors …
This program is a God-send. In the past I used to buy inexpensive CDRs and DVDRs. Now I’m paying the price with a good percentage of my old disks being unplayable. IsoPuzzle is the only program that I found that will consistently recover all of the data.
Further, different drives have fractionally varying alignments. A sector that cannot be read on one drive might be readable on another drive. IsoPuzzle allows you to move the saved-sector index from one drive to use for the continued recovery with another drive. Commandeer as many computers/drives as you can for tough recoveries!
The Internet Archived documentation page: https://web.archive.org/web/20091024204942/http://geocities.com/marsoupilamis/DocEnglish.htm