Solution to find and remove dublicate files easily

When i learned to operate the computer i started blogging but i found my computer very slow. It takes 10 minutes to open the window to begin and i every times i login to my dashboard , accounts, my own blog and hop another blog makes me dizzy of waiting. I am newbie so i thought this is normal to all computer. This is my kid's computer which i bought last year so i am expecting that this is fit for me as newbie. They chosen this because it is the latest pentium so i am expecting that this is normal. I am not a computer genius like my children. They know better than me when it comes to computer, computer parts , computer function and operation and performance or computer problem including xp duplicate files . So i just patiently keep on blogging although the computer is not in normal function. At first i am excited to blog while my kids are in the school but when too much time consumed i found it not fair in my part anymore. I better stopped blogging and do some other things until my son noticed that i never sit infront of the computer anymore, he checked our computer and found the problem, it works very very slow because many duplicate files, pictures or images, music are stored in my daughter's files. She has no time to find and removed them one by one. My son is more knowledgeable about computer problem than my daughter so he suggested that there is a software tool to find and remove dublicate files. And they are very searchable in the internet to find the best software.