Ok,this is what happens i can be working away nicely and then for no reason the pc locks up i cant do anything but reset,after this the bios doesn't detect the slave Hdd it totaly disapears,windows does boot but as i said with no slave drive showing. If i turn the pc off and leave it a while then the drive is back and everything is ok,i did think the slave drive was faulty but i have ran scandisk with full option to find bad blocks and stuff and it comes back clean. This doesn't happen all the time it can go day's even months without incident.
Atm im thinking overheat but can a hdd overheat?,and why is only the one affected they are on top of each other in the case so if one gets hot they both get hot.
I have ran scandisk and it came back clean,i dont think its a cmos batt thing as it does detect one drive and all bios settings are unchanged,as for the power supply failing wouldnt this effect all the pc not just one drive? it is a switching PSU supposed to supply more power when needed.