I don't know if anyone here has laid this out in detail but I can verify that I am running Star Trek Online under 32 bit Windows XP on my Macbook Pro. I was in the same boat with many others getting the Direct 3D error "Could not open D3D Device".
Mind you I am not going to go into detail on getting Boot Camp to work just Google OS X Boot Camp and there are plenty of threads out there describing the process in detail. However, I haven't been able to find a good thread explaining how to resolve the D3D issues so I thought I would start this thread with the steps I took to resolve mine.
First here are my system specs:
Model Name: MacBook Pro
Model Identifier: MacBookPro5,2
Processor Name: Intel Core 2 Duo
Processor Speed: 2.93 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 6 MB
Memory: 4 GB
Bus Speed: 1.07 GHz
Boot ROM Version: MBP52.008E.B05
OS X Version 10.6.2 (Snow Leopard)
Both Snow Leopard and Windows XP installations are up to date with current software revisions / patches.
Once you have Boot Camp working with a supported Windows environment installed and all the Windows Updates and restarts out of the way. These are the steps I took to resolve the Dircet 3D Errors. I have logged at least 6 hours of game time over the weekend in my environment with maximum graphics settings and I have not experienced any issues that I would not chalk up to the fact we are still in Beta. I have not seen any Direct 3D issues at all, game play is detailed and smooth without any graphic artifacts or staggering.
On to the good stuff:
1) Boot into Windows.
2) Insert your OS X Installation Disk.
3) Navigate to the Boot Camp > Drivers > NVidia folder.
4) Run the Setup under NVidiaChipset(OS Version). My Snow Leopard installation disk doesn't have any Windows 7 support but I am betting in these cases you can run the Vista setups. You may want to search NVidia's corporate site for "OS X Boot Camp Windows 7 Chipset Drivers" first. Mind you this is the key to correcting all your D3D problems you MUST install the appropriate Chip Set drivers BEFORE you move on to graphics drivers.
5) If prompted to remove existing drivers answer "Yes".
6) When the NVidia setup is finished removing the current drivers it will prompt you to reboot Windows again.
7) Once Windows has restarted the Windows Hardware Detection Wizard will start along with the NVidia Setup. Close the Windows Hardware Wizard and proceed with the NVidia Setup. I chose to install the NVida Disk Storage Drivers, I doubt that makes a difference and it is the only thing I was prompted for during setup.
8) When the NVidia Setup completes you will have to reboot Windows yet again. Once Windows has restarted everything should appear back to normal.
9) Navigate to the Boot Camp > Drivers > NVidia folder again.
10) Run the setup under NVidiaGraphicsDesktop(OS Version). If prompted choose "Yes" to install the Disk Drivers even if they are older than the ones the system is currently using.
11) start > run > dxdiag and run the Direct 3D tests. They should all pass. If so rejoice!
12) Run the Star Trek Online launcher. Login and cross your fingers!
Hopefully this will resolve this issue for many OS X users. I am a very determined individual (read stubborn SOB) and I was getting frustrated but I refused to be defeated. I am up and running on STO so I hope to see all you OS X users online!
I've been running both champions and ST:O since CB on an iMac running boot camp + XP. Only problem I ran into was when I tried to upgrade the NVIDIA graphics driver, but that's no different than on PCs running with the same card and straightened out when I rolled back the driver.