How to detect two IDE drives with same brand

Put both drives on the same ribbon cable, both drives set to cable select <CS>. the bios will then detect them as primary and secondary.New drives are RAW and therefore not detected by any Operating system until formated. You can use seatools from seagates website to install and format the drive or use disk manager in windows.
Partitioning the drive in Windows XP / Windows 2000 (for systems where this is the 2nd drive in the system).

1. Boot into Windows XP.
2. Open Computer Management and select Disk Management.
3. Initialize the drive.
4. Partition the drive.
5. Format the drive.
6. Assign the drive letter.
7. Initiate changes.

There are two things you need to do
As you have connected the 320 GB, go into the system BIOS , by pressing the F2 key five times on the DELL logo screen, once there press ALT+F keys , to reset the BIOS to reconganise your new hdd. Need to check the same under Primary drive and secondary drive section. If after the reset also the drive is not listsed you may need to install the driver that came with the 320 gb hdd.
Second case : If the hdd is seen in the BIOS but not under my computer, Right my computer icon on the desktop and click manage >go to disk management , you new hdd should show there , right click and create a new partision for the hdd and format the same

http://www.softwaretipsandtricks.com/forum/windows-xp/1610-adding-second-hard-drive-xp-pro.html

You need to set one of the drives to be 'master' and the other to be 'slave'.
This is done by positioning jumpers on the back of the harddrives.
Pretty sure that on the drives is explained somewhere how to position the jumper, for several options.

Good luck,
Please post some feedback.