If the system board BIOS does not detect them on boot up, it is good odds one of them has gone bad (unless of course they are not plugged in and jumpered correctly.) Windows can not detect them as CD-Rom drives, if BIOS did not detect them. But then you said that they are not being detected, so we assume they were working and this is not a simple problem of you setting it up wrong, which should be asked in the hardware forum.