Hi,

thanks BAM but unfortunately nothing worked. here's a little protocol of what I did:

fresh install - nothing passed through
installed vmware tools - rebooted, all good -> shut down (created snapshot)

configured both, gpu and hd-audio devices for passthrough:

01:00.0 | ATI Technologies Inc RV770 [Radeon HD 4850]
01:00.1 | ATI Technologies Inc HD48x0 audio

1st try:
windows boot logo, login screen - 2s later BSOD atikmdag.sys (no driver installed yet, Windows used the WDDM 1.1 driver dated 24.04.2009, v8.56.1.15)
booted into safe mode, disabled ATI 4850 card, booted to normal mode
started catalyst setup, during installation: BSOD atikmpag.sys

2nd try:
restored snapshot
booted into safe mode, started catalyst setup => Failed to load detection driver => aborted

3rd try:
restored snapshot
booted into safe mode, disabled VMware SVGA 3D
booted into normal mode, ATI 4850 shows as "This device is working properly" with WDDM 1.1 driver
started catalyst setup, finished successfully => reboot to normal mode
received popup "No AMD graphics driver is installed, or the AMD driver is not functioning properly. Please install the AMD driver appropriate for your AMD hardware."

activated VMware SVGA 3D => computer needs to be rebooted... done
boot into normal mode, windows logo and BSOD atikmpag.sys

4th try:

restored pre-vmware tools snapshot
booted into normal mode, ATI 4850 shows as "This device is working properly" with WDDM 1.1 driver, VMware SVGA 3D is not yet installed
started catalyst setup, finished successfully => reboot to normal mode
received  popup "No AMD graphics driver is installed, or the AMD driver is not  functioning properly. Please install the AMD driver appropriate for your  AMD hardware."

installed VMware Tools => reboot

boot into normal mode, windows logo and BSOD atikmpag.sys

for now I give up and wait for the 6450 to arrive...

something weird though, after each start or reboot, the vga cooler  goes full speed 4-6 times in ~1s intervals, on shutdown just 2 times
1s on, 1s off, 1s on, 1s off ... and so on - nothing serious, just thought I'd mention it

cheers

Jason

edit: ok, added one last try and a remark