how to make a pic bigger without messing up the resolution?

[SVT Cobra]

i try using my jasc software paint shop pro 8... to resize a picture, especially smaller ones(like avatar sized ones), to MUCH\bigger pictures... however, the quality of the picture gets HORRIBLE; worse as i try to make the picture bigger. even when i try to use the psp's tools to increase sharpness, it still gets worse. what am i doing wrong? how do people make 1024x768 wallpapers with ultra crisp, clear resolution from normal sized pictures? and what software is the best to use? adobe photoshop?

 

[03DOHC]

When you start with a high resolution picture you can make very good quality smaller pictures. The same doesn't apply when making small pictures larger because the amount of data is different. That's why a 5 MP digital camera takes higher quality pictures than a 1 MP camera. And since there's more pixels to start with on a 5 MP camera the picture resolution is better when you shrink them to say 1024 x 768.