How To Convert From Gpt To Mbr?

I have a new empty harddrive that I cannot use.

In Disk Management I can see it as Disk 6 and Healty (GPT Protection).

I understand I can not use GPT disk in 32x and after searching Internet and reading for 5+ hours I understand I can convert and empty disk from GPT to MBR.

I cannot do it in Disk Management because rightclicking the drive gives me no valid options.

When I try to do it in DOS with Diskpart I cannot see the new drive

Options I have for the moment is to buy and install Vista because it works there or to convert the drive in another computer with another OS (that can handle GPT).

Anyone that knows the trick how to do it in my computer?

Thanks in advance!