I have had a quick look at your site and can confirm the script is hard-coded on the page so it doesn't look like there is another script adding the check after loading. Here's the offending code I found (starting at line 229 just after the <body> tag):
<style>
.chromeFrameInstallDefaultStyle {
width: 100%; /* default is 800px */
border: 5px solid blue;
}
#chromeFrameOverlayContent {
top:25%;
}
</style>
<script defer>window.attachEvent('onload',function(){if(window.CFInstall){CFInstall.check({mode:'overlay'})}})</script>
If you remove all of the above then the chrome frame popup should be gone. However, as you can see in the following screen shot the site doesn't look great in IE8 so it'll probably look even worse in IE7 and IE6. Also, I notice I get a javascript error when I visit your site. If you want me to have a look at things and fix up your site I would be glad to carry out some work for you. Just send me a private email if you wish for me to help further.
Thanks,
Jon.