I have the Western Digital VelociRaptor 10k drive SATA. It's about 9 months old now. On three occasions I have noticed quite large chunks of data just disappear off my hard drive. Just now I noticed 200 consecutive pictures disappeared out of one of my folders. I tried to use a data recovery program to get them back but there was no trace of them. Does anyone have any idea what might be going on? I have never received any type of operational error related to my hard drive and I don't have any random unexplained crashes. Is there a program that can test the drive for data retention? If it matters at all, my hard drive is often fragmented for I use a download accelerator that breaks files up into pieces and I often upload large amounts of data to my drive at once. I highly doubt that's relevant though.