*Download from here:
http://sourceforge.net/projects/opencvlibrary/files/opencv-win/1.1pre1/OpenCV_1.1pre1a.exe/download

*Installation and Getting Started Instructions:
http://opencv.willowgarage.com/wiki/#Welcome.2BAC8-Introduction.GettingStartedwithOpenCV

How to configure your project to run OpenCV: (a more detailed explaination can be found in the link above)
after installing OpenCV you need to build it, assuming you installed it in D:\Program Files.
-go to D:\Program Files\OpenCV\_make open opencv.vs2005.sln and build the project.

-create your new project
-in your new project go to Project -> Properties (Alt + F7)
- there go to C/C++ -> general  -> additional include directories and add the following:
"D:\Program Files\OpenCV\cvaux\include";
"D:\Program Files\OpenCV\otherlibs\highgui";
"D:\Program Files\OpenCV\cv\include\";
"D:\Program Files\OpenCV\cxcore\include";

-now go to Linker -> general -> additional library directories and add the following:
"D:\Program Files\OpenCV\lib";
"D:\Program Files\OpenCV\lib\cv.lib";
"D:\Program Files\OpenCV\lib\cvaux.lib";
"D:\Program Files\OpenCV\lib\cxcore.lib";
"D:\Program Files\OpenCV\lib\highgui.lib";

-now go to Linker -> input -> Additional Dependencies and add the following:
cxcore.lib
cv.lib 
highgui.lib

Now you are ready to use OpenCV =]

*Read Chapter 3 in Learning OpenCV. 
 learn how to use IplImage
*on histograms read the end of chapter 6 and the begining of chapter 7.
 learn how to use CvHistogram