To add a little more detail. My mobo is a Asus pn5-t deluxe, Bios 101 (I'll have to double check tonight though). It almost looks as if the hd 4890 stops my sata connections from working!
My suspicion is it's to do with the mobo being for nvidia and the card being ATI! But I'm no expert.
I understand it's not how it's meant to work but seeing as the motherboard passes post with the card installed then after fails to detect my two HDD I was of the assumption that perhaps the BIOS was unable to recognise the RV790 chip on the 4890 and some how that confused the south bridge and hay presto my sata's die a death.
But of course this is all crazy gesticulation on my part.
Ok I started by suspecting it was my BIOS or one of my drivers causing a problem. I didn't really want to clear my BIOS down at first so I tried reinstalling my SATA drivers (didn't work), my chipset drivers (didn't work) and then I re flashed my BIOS to an older version, by the way I was on 1501 and have now gone to 1401 (didn't work). I also (before downgrading) cleared my BIOS by removing the battery.
One thing is though, the Chipset drivers and the SATA drivers are both for Vista 64bit, not 7 64bit so it might not be completely definitive but I think that means I can rule out BIOS problems.
By the way I also completely uninstalled the old card drivers and still no joy.
Tomorrow I'm going to try a complete reinstall, I had hoped to hold off doing this till I got the full version. I don't hold high hopes as when I put the card it I don't see the HDD's so maybe the windows install disk won't either!
Disabling NCQ didn't seem to work, mind you I only tried from within windows (couldn't find any options to disable it in BIOS).
This is a little difficult to follow, if the 9600 works and boots but the 4890 posts and doesn't boot I would suspect you left the Nvidia video drivers intact. If thats right, with the 4890 installed boot into safe mode, if you can remove the nvidia drivers and reboot. It should boot up with standard windows video drivers at which point you can install the correct software for the 4890. good luck
Cheers roonj, sorry for the jumbled nature of my posts, I'm just trying out everything that I can find.
The big problem here is that with the 4890 installed my BIOS doesn't see any of my (now) 3 HDDs so I can't even boot into safe mode. The other day I found a tool that help clear drivers completely so I used that and then installed the 4890 but the same happened, no HDD were found in BIOS!
I've also posted on the Asus forum to see if their techs could help, the only response I got was from a guy who had had the exact same problem whilst trying to install a ATI 4850! Maybe it's an inherent fault with this motherboard.
But it's not all doom and gloom, I have got it working. If I leave my 9600 in the primary PCIe slot but don't feed it power (leave the 6pin out), then install the 4890 in the bottom PCIe slot (third slot), it boots into window recognised my 4890 as the primary display device and runs games without a hitch (at least so far).
Ignoring the obvious stupidity of this set up there are two big problems with doing this. The first is obvious, I can't sell my 9600 so I'm around £40 out of pocket. Second, the 9600's fan spins at full speed constantly which is pretty loud.
I installed an older (8500gt) passively cooled geforce this morning but, as it didn't require extra power to run, my pc used it as the primary device! Tonight I'm going to see if I can get that configuration working. maybe if I deactivate it windows will default to the 4890.
I found no solution but Asus did offer to repair my motherboard, something I didn't take them up on as I had to send it to them at my expense, I did appreciate the offer though. Instead I just paid an extra £50 for a GTX 275!