My PC have 3 harddisk, one of them would like to disconnect (the harddisk drive letter disappear/no harddisk found in computer management) while the PC is power on and running. It's disappear randomly..it give me many trouble. During this problem I have to open the case and disconnect/connect again the IDE/power cable then it's running normally. Also it can't detect it when sometimes power on the PC(but not everyday).. My PC just brought for a year, everything is new except the harddisk is used for 4 years, but it is working fine with no any problem(except it is disconnect) I have this problem again when in my old PC.. What problem ? virus or it's aging problem of hardware?