Setting up DVI on a Dell desktop

I've recently been playing around with a three year old Dell E520 desktop with a nVidia GeForce 7300 LE graphics card.
The machine has been in only intermittent use during its life and is likely to remain like this.
First thing I did was to step up the RAM from 1GB to 3GB which was very simple and cheap (€37 from Crucial for 2GB of DDR2 PC2-5300 including delivery).
Now even though this machine has both VGA and a DVI-D video sockets, it has always operated on VGA only because that's all its monitor was capable of.
However, I had also acquired a larger LCD screen and wanted to fully avail of the sharpness of DVI at my new 1600x1080 resolution.
But, I just couldn't figure out how to get the DVI cable connection to work.
Finally, after extensive Googling, all became clear.
Now, I started out with both the VGA and the DVI cables connected between the computer and the monitor.
The first step is to enable DVI by continually pressing the left-most button on the bottom
of the monitor.
Now, disconnect the VGA cable.
Next reboot and everything should be fine.
Actually, what I found here may well have some bearing on another problem we had with a larger Dell machine (XPS 9200) that we just couldn't stop from going into powersave mode.
With the E520, when only the DVI cable was connected, the monitor wen into powersave immediately after booting.
I'll try some experimentation tomorrow to see if I can resolve the 9200 issue which I had previously put down to a damaged graphics card.