Here are a few tips which I've come up with by putzing around a bit with VirtualBox:
When VirtualBox starts up, if you have the option set, it will check for a new version. If one is available, update it! The Direct3D extensions get updated all the time. As a result, these updates make the game run much faster and more reliably. Be sure that whenever you update VirtualBox itself, don't forget to update the VirtualBox Guest Additions install in your Windows guest, following the steps Miyuki outlined near the top of this thread.
Get a virtualization-capable processor
A processor with hardware virtualization support benefits not just execution speed, but also robustness. In my testing when I disabled the virtualization support for the VM, while I was simply moving around, the VM I was playing in rebooted itself.
Just about all brand-new processors support them by default nowadays, including the entire Intel Core iX series as well as all AMD processors (except for most Sempron processors).
Need to know whether your processor has hardware virtualization support? Pick up a recent copy of CPU-Z
and run it. Look in the "Instructions" section on the first page. If you are running an Intel processor, you will see "VT-x"; if you have an AMD processor, it'll show "AMD-V".
Also note that you will need to turn on virtualization support in your computer's BIOS.
Get faster memory
This item ALONE can help speed your VM execution dramatically. On my machine, I went from DDR2-800 to DDR3-1333 (my machine supports both types, but only one type can be in use), netting a very noticeable speed increase. This is especially true if your current memory speed is slower than your processor's front-side bus (FSB) speed. In my case, I'm running a Core 2 Duo E8400, whose FSB is 1333MHz.
I hope these tips will help you to get Trickster running faster and more reliably in a virtual machine. Good luck and have fun!