Problem Solved!
Thanks for the input and suggestions. As I mentioned in my first post, Vista 64 would not recognize that a third GPU was in the system. No matter how many times I unistalled cards and drivers, Vista would not recognize the third card which would prevent the installation of drivers for the third card. I had confirmed that each card individually functioned and that I had the latest drivers for GPUs and MB. I found an almost obscure post on on the NVidia forums with an installation method that worked for me. Here is what I did:
1) Turn off computer
2) Remove GPUs except for PCIe 16X1
3) Reboot
4) Remove GPU drivers
5) Reboot
6) Install GPU drivers (I used 180.48-latest WHQL)
7) Shut Down
8) Install GPU in PCIe 8x1
9) Reboot and windows will install driver (confirm 2 GPUs in Control Panel)
10) Shutdown
11) Install 2 -Way SLI bridge
12) Reboot and confirm that SLI option is available in NVidia panel
13) Shutdown
14) Remove 2-Way SLI bridge
15) Install 3rd GPU in the PCIe X16_2 slot without SLI bridge
16) Reboot and windows will install driver.
17) Confirm 3 GPUs are avaialble in Control Panel. In my case, the GPU from PCI Express Root Port 9 was now missing (PCIe 8x1 slot)
18) Shut down
19) Install 3 Way SLI bridge and reboot
20) Windows bubble may inform you that SLI is available
21) Confirm you have 3 GPUs in Control Panel (I did)
22) Confirm that 3 Way SLI is available in the NVidia Panel
I know this sure sounds like a convulated method for installing 3 way SLI on the UD5 Mobo but it worked! The strange part was losing the second GPU in PCIe 8x1 and then having it re-appear when installing the 3-way SLI bridge. I