Judging by the signature it seems that both hdd's are SATA right?
If the hdd's are ATA and are on the same IDE channel might wanna try and separate them. One on each channel.
If that doesn't solve the problem might wanna try a different power cable for the hdd.
And if that doesn't solve the problem, then it's possible that the Maxtor is dying.
Question though. After Maxtor "dissapears", and you reboot , does it shows in the POST ( if you are able to see the POST of course)?
If the hdd's are ATA and are on the same IDE channel might wanna try and separate them. One on each channel.
If that doesn't solve the problem might wanna try a different power cable for the hdd.
And if that doesn't solve the problem, then it's possible that the Maxtor is dying.
Question though. After Maxtor "dissapears", and you reboot , does it shows in the POST ( if you are able to see the POST of course)?