Dual Monitor on 2 VGA displays (help!)

[magicstick5]

I have a Dell OptiPlex GX620 mini tower and am looking to connect a second monitor to it.
Both monitors are VGA and the graphics card (ATI Radeon x600 256mb dual Monitor) has a y cable with 2 VGA connectors. I have successfully connected both and they display content but Windows only detects it as 1 display and therefore, I cannot expand the whole desktop along both displays.
How would I go about fixing this and getting a dual monitor setup working?

Thanks,
magicstick5

 

[Petrossa]

You need to plug each monitor to a separate output on the card for your system to recognise it as a dual monitor setup.
Currently you are only using one output and mirroring the picture onto the 2 displays.
You can use a DVI-VGA converter for the 2nd output.