problem with hard drive again

with valued help from a member on this forum i managed to get my dell dimension 9100 to reconise my second hard drive i configured this hard drive with data lifeguard tools when i look in computer management it says the drive is working properly and is healthy i can access the drive and write to it with no problem..however when i swich off pc and restart it it does the same thing as before freezes on dell load page for about 1 min then tells me there is no boot drive available i enter set up mode and in drives it tells me no drive reconised...sata operation is set to  raid autodetect/ata..so i tried to swich to  another mode  autodetect/ahci now when i save and quit it starts to boot but resets itself i then press f2 and the bios says my two hard drive are there so i change back to autodetect/ata it then loads no problem...so it seems to be problematic when i power off any help would be great...