My hardware:

Cheap Acer Extensa Destkop. 4 Gb. Win7 Home Premium 64 and Kubuntu 12.04 64. HD3200 integrated graphics.

This hardware works fine under Linux. Later I added a Sapphire HD 6450 board and it also works fine with ATI proprietary drivers. Screen cable connected to VGA output of the additional PCI HD 6450 board. Screen is 1920x1080 LED.

Yesterday I added on this same PC a Win7 Home Premium 64.

First, it can't offer a better screen resolution than 1400x1050. 

Ok, i suppose it will do better after installing Catalyst. Anyway, I check the hardware seen by Win7 and discover that it only mentions a HD 3200. No trace of another board. Shutdown and restart Linux for a check: the HD 6450 is there and working. OK, let's go on...  Back to Win7 and installation of Catalyst 13.1.  I'm not experienced with it but it seems to do it all by itself. Installation completed without warnings or error messages.

Restart computer and.... blue screen of death!  It keeps restarting in a infinite loop....

I googled a bit on this issue and only found that it is mandatory to uninstall any previous ATI drivers present on the PC. Not my case, as this was a new installation of Win7.

So what?

First time I find a piece of hardware installing smoothlessly under Linux and giving troubles under Windows...   The times they are a' changing.....

Many thanks in advance to anyone who will help!!!

Franz

1. Clean the current video drivers from windows.

2. Disable the IGP in the BIOS.

3. Boot windows and install drivers for the 6450.

Why it doesn't work under windows: Current display drivers can't handle legacy cards. Older drivers could, but you have a mixture as windows update overwrites part of your driver installation.

Why it works under linux: 6450 is using the proprietary drivers. 3200 is using open source drivers (has no choice anyway). There's no conflict as linux (and X) is more intelligent than windows.

CPU: AMD Phenom II X4 810 @ 3250MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 850/1100MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 95 x64 Edition, Lubuntu 13.04

CPU: Pentium 4 Northwood S478 @ 3200MHz | RAM: 1,5GB DDR 400| MoBo: Gigabyte GA-8S661FXMP-RZ | GPU: Abit Geforce Ti 4200 | Display: Dimarson 19" CRT | PSU: Noname 400W | OS: MS Windows XP Pro, Lubuntu 12.04

So I'm guessing that you got Win7 to boot and are you running a duel boot system?

Did you update Win 7 first i.e. SP1 and any new updates? If not then try that first. Also when you update Win 7 it will install drivers for your card. So you need to uninstall the windows driver.  To insure you have clear out all the old drivers use Driver Sweep 3.2.  Then install the drivers from AMD.

I'm not sure if the HD 3200 and the HD 6450 will work together in crossfire. So you might what to check on that. So you might have to go into BIOS and disable the on-board Graphics. If the HD 3200 will work in Crossfire still try and install the HD 6450 first then try and to get you HD 3200 to work.

I know I've seen this problem else where on an other forum. But it's been some time. Hope this helped out some.

Edit: Go with Eydee

GA-MA-790X-UD4P AMD Phenom II 555 BE @3.2 unlocked to 4 cores
Corsair H50 (CPU Cooler) PS Antec EW 750 /Case Antec 900 II
Asus EAH5770 CUcore/Super Talent 8GB DDR2 6400/LG HL-DT-ST DVD/CD Burner,Alpine 3 1/2 Floppy /Hitachi 250 ,WD 250 /Ati High Definition Audio, Creative SB Titanium X-Fi. OS Windows XP 32 Windows 7 64 Ultimate.

Thank you all for your answers and suggestions.

It works now.

Now I wonder why among all the junk printed in manuals there is NOT a simple instruction such as " disable from bios your integrated graphics card, if present".