How to get process's user and domain without WMI

[DaveMidgley]

I am trying to get the user name and domain of a running process. I can do it using the WMI, but this has various problems (it's slow, it needs to run wmiprvse.exe). There must be a way of getting this information without using the WMI - does anyone know it? (I'm using C# under .NET2.0, but that should be irrelevant, any answer is going to involve a p-invoke, I'm sure)