Cannot detect slave drive???

Hi,
When I opened the computer cover of my CPU,I realised that the ribbon cable is unplugged from my hard disk.When I plug it back and restart my PC,I only see my C: partition.Initially the slave drive was named D but I can see it under 'My Computer' nor 'computer disk management.Can anyone please tell me how to configure the CMOS or BIOS settings to enable windows to detect this slave drive.How do I assign a letter to it and will my data be lost?Thank you for your assistance.