My operating system is xp pro, i have norton 2004 installed and i've completed live up date and done a virus scan with no faults found. now and again i've been get messages say i have corrupt or unreadable files and i should do a disk check i also get this sometimes when i do a disk defragment, when i do a disk check it deletes orphaned files and when i reboot it stops and says disk read error. i've changed my hard drive and my mothherboard as requested by the computer repair shop but i'm still getting the same problems. the software that i'm using is the same software that i've had on for some time and i've also used that software on other computers without any problems. this there any thing that can be causing this?