Hi PoD
The best thing to do is to replace the DVD rom with a DVd writer unless you want to do DVD to DVD copies "on the fly" which isnt a good idea.
Each IDE channel can only support 2 drives so typically you have a primary and a secondary IDE channel so you can have 4 drives.
I think the new mobo that you got was SATA, did you use SATA hard drives or did you stick with IDE ones ?
If you used SATA then you would have some spare capacity on the IDE channels.
You can also buy a PCI IDE controller card which would allow you to add up to 4 more IDE drives but I think you would be better off just swapping the DVD ROM for a writer I suggested earlier
Ps I will sort out your login problems shortly for you
Edited to add that it should be sorted now, check your PM for this account for details