You can change the size or resolution of a digital picture by changing:
The number of pixels. The resolution, or sharpness, of a picture is determined by the number of pixels it has. More pixels improve the resolution of a picture, which allows you to make a larger print without reducing visual quality. Keep in mind, however, that the more pixels a picture has, the larger its file size will be.
The file size. The amount of space a picture takes up on your computer and how long it takes to send as an e‑mail attachment is determined by the picture's file size. Although more pixels often means a larger file size, the picture's file type (JPEG or TIFF, for example) usually has more to do with file size. For example, a picture saved using TIFF will be much larger than the same picture saved using JPEG. This is because JPEG pictures can be compressed, which makes the file smaller at the cost of slightly lower visual quality.
If the picture isn't already a JPEG, you can usually save a significant amount of space by saving the file as a JPEG, and then deleting the original TIFF version from your computer. For information about saving a picture as a different type of picture file using Paint, see Change a picture's file type (file format) using Paint.
Open Paint by clicking the Start button , clicking All Programs, clicking Accessories, and then clicking Paint.
On the Home tab, in the Image group, click Resize.
In the Resize and Skew dialog box, select the Maintain aspect ratio check box so that the resized picture will have the same aspect ratio as the original picture.
If the Maintain aspect ratio check box is selected, you only need to enter the horizontal value (width) or vertical value (height). The other box in the Resize area is updated automatically.
Do one of the following in the Resize area, and then click OK:
To resize your picture by a certain percentage, click Percentage, and then enter a percentage to reduce the width by in the Horizontal box or a percentage to reduce the height by in the Vertical box.
To resize the picture so it's a specific size, click Pixels, and then enter a new width in the Horizontal box or new height in the Vertical box.
Type a new file name in the File name box, and then click Save.