large capacity hard drives.

I have a question concerning large capacity hard drives, specifically, Western Digital 200GB drives. I have a user at work who installed two of these drives in a Dell Dimension 4XX PC to be used as a server. He partitioned the drives with Partition Magic. He says that after about a month or so, both drives mysteriously lost one of the partitions. Dell PC has latest bios. Ran diagnostics on drives, no errors. Any ideas? Thanks.