I like to run my computer with as few processes and services as possible.

Okay, so I understand there might be a few more processes I have to run to keep my graphics co-processor included... I can play with that later. What are the dependencies of boinc? Or did I say that wrong? Boinc is a dependency of which processes?

So... what are the fewest processes and services needed to be running for boinc to be fully functional?

I am using XP and XP-pro on my extra computers dedicated to boinc.

Depends on which BOINC you're talking about. Since you posted in the API forum, that makes you a programmer, right? So then you must mean the BOINC back-end, right? ;-)

That requires Linux. So there.

If on the other hand you're asking about the client, the thing that steers the science applications in the right direction, then you need at minimum Windows XP.

For the GPU to work, it requires drivers made by the GPU manufacturer, not by Windows.
If it's an ATI/AMD GPU and you want to run OpenCL applications on it, you require Windows Vista or above. This is a requirement by the GPU manufacturer, not by BOINC.

BOINC should be installed as a user installation, not as a service --aka protected application execution, as then the GPU detection won't work.

Other than that, check with the project of choice what OSes they stock applications for. Most do Windows, but some are Linux only.

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