Difficult to download iTunes

I used my Personal Computer which is Windows XP, Version 2002, Service Pack 3. As I tried to download iTunes most of the times since I bought iPhone 4 on late April, 2012. But all the efforts does not works. Sometimes the computer tell me "the application is incorrect" and sometimes ".exe is not a valid Win 32 application." There is no Music, Video in my iPhone now, so I want to enjoy Music and Video with my iPhone asap. All my iCommunity mate, Please help me.