Two possiblilities come to mind. Either some program improperly wrote to a portion of that disk, corrupting the data that is there (I think that this is unlikely). If the program that "owned" that data had a bug, then it, too, could have written bad data. In both of these cases, the actual disk hardware is still good. A hard drive has platters with magnetic material on them. The head that reads the magnetic material rides over the platter at a very, very small distance. If a speck of dust, that has been floating around innocuously for the last year or two, suddenly gets caught in the wrong place by the head, it can rip out a bit of the magnetic material. Formats and disk checks can sometimes repair this problem if the dust and chip get lodged in a harmless place. If they do not, then, over time, the number of bad spots will increase. It is also possible for a piece of magnetic material, that is not stuck well, to break loose and cause the same type of problems. These kinds of problems were more common in the past then they are today. Dean Kukral ----- Original Message ----- From: Hugh Vandervoort Sent: Friday, September 02, 2005 1:54 AM Subject: Re: [PCBUILD] Disk IO Error After much fiddling, I determined that one of the RAID disks had become corrupt. (How does that happen?) <snip> The NOSPIN Group Promotions is now offering our special coffee mugs and mouse pads with the PCBUILD logo... at a great price!!! http://freepctech.com/goodies/promotions.shtml