I got my 120gb WD drive! But where to connect? I have a 40gb drive with OS on my primary master that I'd prefer to keep for simplicity. I also have a DVD/CD-RW combo drive (not sure if thats primary/sec yet). So where should the CD and 120gb drives go?

The way I would do it would be to leave your 40GB as primary/master, set the 120GB for primary/slave. Have the combo drive as secondary/master and the cd-rom as secondary/slave. WD drives, I have found, do not work well jumpered as cable select so jumper them the way you want them set. Give that a try and if it doesn't work, move them around until it does.

Harddrives should be on the same cable, since they are faster than DVD/CD-RWs (normally). The transfer rate wouldn't be faster than the slowest item. This would be the DVD/CD-RW (usually ATA33, unless they have become faster recently), while the HDs are probably ATA100 or ATA133. So you would get a significant performance drop by putting HDs and DVD/CD-RWs on the same cable...

Stig