i fixed this source up to work with vista and xp better
if you would like to try the compiled version click HERE
Code:
//Based off of McGraw-HiLL's Gallons to liter converter Edited By SonniE (WWW.codinghs.COM)

#include <iostream>
using namespace std;
int main()
{
double gallons, liters;
cout << "Enter number of gallons: ";
cin >> gallons; 
liters = gallons * 3.7854; // convert to liters
cout << "Liters: " << liters << "\n";
system("PAUSE");
return 0;
}