I have two drives that are the same model and capacity. They are Western Digital 800JB 80GB disks. One holds the OS, the other holds my data files. Today, I noticed that the capacities for both are reported differently in Windows Explorer -- even though they are the same model. The OS drive has about 10MBs more than the Files drive. Is this normal? Could I possibly have some kind of virus on the Files disk? I did once discover a virus on the files disk. But could I have a Master Boot Record virus? I ask, because I ran my anti-virus software, NOD32, and received this message. Error occured while scanning MBR sector of the 3. physical disk. Error reading sector.