Question: How can I determine all processes in the child's Process Tree to kill them?

I have an application, written in C# that will:

1. Get a set of data from the server,
2. Spawn a 3rd party utility to process the data, then
3. Return the results to the server.

This is working fine. But since a run consumes a lot of CPU and may take as long as an hour, I want to add the ability to have my app terminate its child processes.

Some issues that make the simple solutions I've found elsewhere are:

• My app's child process "A" (InstallAnywhere EXE I think) spawns the real processing app "B" (a java.exe), which in turns spawns more children "C1".."Cn" (most of which are also written in Java).
• There will likely be multiple copies of my application (and hence, multiple sets of its children) running on the same machine.
• The child process is not in my control so there might be some "D" processes in the future.
• My application must run on 32-bit and 64-bit versions of MSWindows.

On the plus side there is no issue of data loss, a "clean" shutdown doesn't matter as long as the processes end fairly quickly.