Question

Is there a way to determine the amount of memory installed on a computer running
64bit windows 7, using VS2010 C?

The app I am running is a Windows 64bit app, with
a UI written in c#, which calls a dll written in C. The call to get the installed
memory has to be done from the C code, not the c#.

Answer 1

Use the GlobalMemoryStatusEx function:

MEMORYSTATUSEX memInfo = {sizeof(memInfo)};
if (GlobalMemoryStatusEx(&memInfo))
{
    printf("Total installed physical memory: %lld bytes\n", memInfo.ullTotalPhys);
}