If you saved it "small"...that is using not a lot of memory, there is no way to get more memory.
You can enlarge the picture but it will be grainy, not enough pixils to make it clear.
Linda C

Yep, what Linda C said. As they say, garbage in garbage out. There is some really expensive software out there that "might" do the job. Other than that, the ONLY way to do it is incrementally:

You most likely have a 72 dpi jpg from the web, let's say pixel dimensions are 163W x 139H or 2.264 inches x 1.931 inches. First, research the web again to see if you can find the same image with larger pixel dimensions. If that's a no go or if you find something but it still needs to be larger and you are using Photoshop follow these directions:

Go to Image>Image Size

Under the area labeled "Document Size" in the pop up window change the "Width" and "Height" to "percent" instead of "inches". Change the percentage from 100 to 110 in each direction. DO NOT CHANGE THE RESOLUTION YET. Be sure to have the "Constrain Proportions" and "Resample Image" radio boxes checked. The latter option should be set at "Bicubic".

Repeat the 110% upsizing until just before the image takes on a nasty pixelated haze and looks distorted. After doing this 5 times in our example, the pixel dimensions will be 263W x 224H or 3.653 inches x 3.111 inches at 72 dpi.

If you wish to use the image for printing purposes, go to Image>Image Size.

At the bottom of the pop up window, uncheck the "Resample Image" radio button and change the "Resolution" field to 300 pixels per inch. When you do this, the width and height inches field will change automatically. The size related in those fields are the highest you can go without the nasty pixelated distortion for printing purposes.

You can try some of the blurring filters, but that really won't get you where you want to go.

HTH

Bump

The best way that I know of is to print the picture out, then put it on a flatbed scanner, scanning it larger. It's the only way that I've found where it will keep the image clean and not grainy.

What I would do is make sure your digital camera is set to the largest size so that when you take more pictures you won't have this problem again.

Also remember when you save your photos to places like Photobucket, the resolution is GREATLY reduced. I have a friend who took all of her family photos and saved them in a place like this and then deleted the originals from her computer to save space. Yep, she was shocked when she tried to print things!