Parition Mistery

[87325is]

I have a c and a d drive which i created with partition magic.

ever since i have in stalled perfect drive which crashed once, the d drive disappears sometimes. One time was on a reboot and the other was on office install.

I have run check disk and tried to recover the partition. Nothing worked so i recovered from a day old back up both times it disappeared.

When it disappears i have to recreate the partition it is labeled unused space when it goes bye bye.

anyone have an idea of what might cause this? antivir comes up with nothing.