I absolutely love fluid layouts, Hate going on my 42" tv with computer and have a layout being just 1/10th of the screen size.
Open the styles.css file of which ever theme you choose,
Find the Body section
Add in this: min-width:1000px;
After padding:0;
End result:
Code:
body {
background-color:#e0e0e0;
font-family:Arial, Helvetica, sans-serif;
font-size:1.0em;
margin:0 auto;
padding:0;
min-width:1000px;
}