UDMA on or off?

In my Dell 4300, the BIOS currently has the IDE UDMA setting as OFF

I am replacing an old 20GB drive with a newer one ( say 120GB IDE).

I had assumed I should be turning on ON.

However I read conflicting advice ie

• OFF: "Make sure that your BIOS settings are not configured to force faster UDMA modes"
• ON : "UDMA (fast access for your IDE drives) off ..I can't see why you would ever choose this option. The performance is terrible without it."

Whats the correct setting for a newer drive?