Sorry if this has been already posted.
Taking the picture
1.Press Prt Scr when you want the screenshot
2.Click Start->Programs->Accessories->Paint
3.Click the top-right button on the Paint toolbar
4.Right-Click in the background(white)and click Paste
5.Remove unneeded parts
6.Click File->Save As and type a name
7.Go to the File Type drop down box(right under File name)and select JPEG(or JPG)
8.Save and follow hosting instructions
Uploading the image
1.Save to computer
2.Go to http://imageshack.us/
3.Click Browse and find where you saved the image
4.Click the image file and click Open
5.Click Host It
6.Copy the link in the Direct Link To Image box
7.Wrap the url in IMG tags on the top bar in the reply box
8.Paste the link between the tags and hit OK
9.Put in neccessary text for the reply and hit Add Reply