u can use photoshop, paintshop pro, irfan view etc.
in photoshop, select the whole pic [Ctrl+A] and select resize image. put your desired pixel. select the compression ratio and finally click resize. image clarity is well balanced.

why don't you try with this? open ms-word, insert the picture, edit the picture size, copy and paste it in Windows Paint, save the image as .jpg or .jpeg format. do you like it? 8)