Help on Portfolio

So i am making a portfolio for college, i have a section for all my images, the section consists of four images and each one has a mouseover image, i want to make those images open a new browser window, i have tried doing this with success, however whenever i put in the java script the mouseover image doesnt work anymore. this is what the lines look like, tell me if im doing something wrong. I would greatly appreciate this.
<A href="#"
onmouseover="changeImages('index_30', 'images/index_30-over.gif'); return true;"
onmouseout="changeImages('index_30', 'images/index_30.gif'); return true;"
onmousedown="changeImages('index_30', 'images/index_30-over.gif'); return true;"
onmouseup="changeImages('index_30', 'images/index_30-over.gif'); return true;">
<A href="javascript:createWindow('url','name','features')"><img name="index_30" src="images/index_30.gif" width="275" height="125" border="0" alt=""></a></td>