I have used three monitors under XP for years (using two video cards) but when I bought this (HP XW8200) workstation I decided to give Eyefinity a run so I could do it with only one card.
This machine presented some challenges, I wanted to do Eyefinity 6 but my Adaptec RAID controller blocked me from using a double bay card. I did some research & found that XFX had begun making a single slot Eyefinity 5 card (the 5770), so after some digging, I got one. I wanted the capability of 5 monitors, but currently am only using 3 so I ordered three Accell brand mini displayport to DVI (active) adapters, & am sure I have the right ones because I got the part number from XFX support.
I use two widescreen monitors (a 24", a 21", both Viewsonic), and a 20" 4x3 white box monitor (but that uses Viewsonic parts, as I learned when I had to recap the power supply). I am not sure how to describe the symptoms I have because it is not real consistent, but sometimes the computer will have already ran most of the POST screen before any of the monitors display (& POST takes a long time on this machine because of having to boot the RAID kernel). But ALL the time, after the computer boots and finishes with the "Starting Windows" screen, I get a black screen that appears on all three screens in lieu of the logon screen.
If I let it sit there awhile, apparently Eyefinity "finds" my primary monitor, & I can log in, and from there it is perfect. Also, when Windows turns my monitors off after a period of activity, I get the same thing. I can wiggle the mouse and the secondary monitors wake up, but the primary one is still black & am unable to log in.
There are no machine BIOS upgrades available, and I honestly am not sure about BIOS updates for the card. I am pretty sure that my cabling is ok, since once I am in Windows it works great.
Based on some forum threads I have looked at, I suspect that this XFX card does not like Viewsonic monitors, or at least certain models of them. I am planning on buying three new monitors very soon, but I have decided on HP ZR24W's & after what seems like a box of stuff every day from Newegg, I can't swing it this month so I was hoping for a workaround.
If anybody can shed some light on this, that would be awesome.
PS- I have a ticket in with XFX support as well, but they have not responded as of yet. Will post if they have any useful information.