multithreaded c++ question

I'm using VS.net 7.1 on Windows XP.

I have a class that hold a container of doubles. One function (foo) for
the class calls a sub-function (bar) for each of the doubles. I'd like
to multithread foo so that the bar sub-functions can run on multiple
threads. I'd like to imlpement this with _beginthreadex as I'm using
std::vector. Please provide some working code around the following details:

#include <windows.h> // for HANDLE
#include <process.h> // for _beginthreadex()
#include <vector>

using namespace std;

class A
{
private:
    vector<double> v;
    double d; // some other variable common to each thread;
    double bar( double x );
public:
    vector<double> foo();
};

vector<double> A::foo()
{
    vector r( v.size() );
    for( int i=0; i<int(v.size()); ++i )
        r[i] = bar( v[i] );

    return r;
}

double A::bar( double x )
{
    double r = x*d; // some function using x and d
            // obviosly more complicated in the real code...
    return r;
}

Now what I'd like is for multiple instances of bar to run on my two
cores. Can you help me please?