How do I get my desktop settings back to default

Hi

Hope someone can help - I have a new Dell Inspiron 1545 with MS Vista ( which I have never used before ) Initially eveything was fine but without my changing anything my screen view has changed such that everything looks like it is stretched too wide and is distorted. I can't find any setting to get this back to normal and in the process of trying have managed to change something on my desktop so that all the icons that were preloaded in the dock bar have now moved onto the desktop and I want to get rid of them. Can I just delete them or does that mean I am deleting the related programs ? I didn't want the dock on but although I kept following the command to hide it it kept appearing again  everytime I restarted. I have also managed to lose the clock and weather which was down the right hand side and can't work out how to get that back again  - any advise would be much appreciated