Hard drive disappering

My new Wd 320gb internal hard drive (Sata )disappears when I connect DVD writer even from BIOS. But I somehow was able to install windows 7. All part are working fine.I tried them separately and they work.
Configuration
Motherboard-Intel DG41RQ
1GB DDR2 RAM
2.7 Intel Dual core E5400 Processor
320 Gb WD internal Hard drive (refurbished)
THANKS
 
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