This means the built-in error checking noted a bad block of data. Discs follow this for data: 32 bits of data, 32 bits of CRC that the data MUST fit to be valid. Without this, you'd never know that the data was bad. Due to the nature of CRC, if you have low-level access, you can attempt to reproduce what the CRC thinks the value should be... but the CRC is probably also incorrect, so you've got 2^32 possible values of that 32-bit chunk of data. Unless this data is truly critical (if so, you've got other backups, right?), I'd consider it a loss and move on.
Something I'd always considered doing was writing a program that could give me "double capacity" on CDs by eliminating CRC... but (1) I don't know if I can eliminate this with software (hardware could be hard-wired to do it) and (2) It would NOT be a good idea because you'd never know if your data's good or not.
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Primary
CPU: Athlon 64 X2 4400+ Mobo: Biostar N4SLI-A9 RAM: 2G Crucial (DDR400) Video: eVGA GeForce 7900 GTX (512M) Audio: HDA X-Mystique HD(s): Maxtor 300G SATA2, Samsung 400G SATA2 OS(s): WinXP x64 Pro, Vista x32 Ultimate, Gentoo x64 Monitor(s): Primary - 19" Flat Panel (1280x1024) Secondary - 19" Flat Panel (1280x1024) Tertiary - Zenith 42" Plasma TV (1024x768 res)
Many other machines... sig too short