Just right click on the icon you want, then save it to a file

on your hard drive. Then right Click on the icon you want to change

go to proporties and then change icon. 

Click browse then find the file where you sved your new icon,

select your icon and then your done!

To change the My computer Icon, trash can or My documents icon:

Right click on your desktop, Go to proporties,  Then click on Effects,

Select the icon you want to change, Then click Change Icon, Then

Browse for the file where you saved your  new icon, and select it .