Ok, I have a Dimension 8100, running Win ME.  I had an 80 gig western digital hard drive, but it's been filling up so I got a new one to go with it.  My plan was to install the new HD (same HD type/model) as a slave, copy important files over, and then reformat and reinstall the OS to my original HD (cause it had a virus/various problems).  Well, it wouldn't recognize the slave drive, so I installed the OS to the new HD with the original HD unhooked.  I then set them both for cable select, with the IDE cable in the correct spot, blue on mobo, gray on slave, black on master, and both HD's are recognized in my Bios, master as type 41, slave as 'auto'.  Well, in 'My Computer', only the new HD is showing up, labeled C:  When I go into my system manager in control panel, I can look at Hard Drives and see that both of them are showing as there.  When I go into the Western Digital data lifeguard tools program, I view Hard Drive information, and it shows them both there, but the original one has no letter to go with it.  It also shows them both on the Primary ATA controller and nothing in the Secondary ATA controller.  I assume that I need to get the original hard drive to be read through the secondary ata controller, but I'm not sure.  Also, in my control panel > system properties > device manager > hard disk controllers > Intel ultra ATA storage controller > properties > settings area, I have selected the "Both IDE channels enabled" in the "Dual IDE channel settings" drop down menu.

So, thats what I've thought of and still no luck getting it a letter and showing up in 'My Computer'.  I'm stumped.  Any suggestions/ideas?