alibegoa

Hello all This is the problem I have. I noticed that when I play songs on my computer they usually have different volumes. So I downloaded wavepad and tried to normalize them all to 100%. This did change some songs but still some songs play louder on my speakers then some others. Now if I amplify some of them to say 150% the difference becomes less noticeable. But how do I know how much % to amplify all of them exactly to have them all at the same level? I would really like to have them all at the precisely the same level.