I have an ati radeon hd 6970 hooked up to my computer. I bought two dvi to vga adapters for the monitors that i have and when i hooked them up, only two of them worked. I have the middle monitor hooked up on hdmi and the right monitor hooked up on the vga to dvi adapter, but the monitor on the left doesn't get any signal even though im using the same adapter as the monitor on the right. I would love to know what is going on
I need to know the exact maker and model of your 6970 in order to tell you exactly which adapter you need to get the third monitor working. But you should be able to figure it out. Some 6970 cards have full-size Displayports(DP), while some have miniDP.
It sounds like your two side monitors need VGA. So depending on whether your card has full-size DP or miniDP you will need an ACTIVE DP (or miniDP) -> VGA adapter.
That 2nd one isn't listed by amazon as being "active" but it is listed by AMD as an active adapter. It is active, just not listed as such. Anyway you only need one of those adapters to make your third monitor work. Figure out whether your 6970 has miniDP or regular DP and get the appropriate ACTIVE adapter.