>>Is there a place in the registry to do that? Or any other way?
>>
>>I don't want for the user to be able to open another instance of Explorer.
>
>
>Sorry the title should have been "How to disable CTRL+N" :-(

I use the following code in body onkeydown() event:

function body_onkeydown() {

// ALT combination
if (event.altKey == true)
{
switch(event.keyCode)
{
case 36: // ALT+HOME
event.keyCode=0;
event.returnValue=false;
event.cancelBuble=true;
alert('Please click the Home button.');
break;

case 37: // ALT+LEFT ARROW
case 39: // ALT+RIGHT ARROW
event.returnValue=false;
break;
}
}

// CTRL combination
if (event.ctrlKey == true)
{

//if (event.keyCode!=17)
// alert( 'keyv' +event.keyCode);

switch(event.keyCode)
{
case 11: // Ctrl+K
location.href='GetTable?Table=KLIENT';
break;

case 33: // CTRL+Page Up
Prev();
break;

case 34: // CTRL+Page Down
Next();
break;

case 35: // CTRL+end
case 36: // CTRL+ home
return;

//case 66: // CTRL+B
//case 68: // CTRL+D

case 69: // CTRL+E
location.href='GetTable?Table=DOK&Form=DOKLSTL&Type=G&SubType=L'
break;

//case 70: // CTRL+F
//case 72: // CTRL+H
//case 73: // CTRL+I

case 77: // Ctrl+M
AddRow();
break;

case 78: // CTRL+N
// disable ctrl+n
break;

case 80: // CTRL+P
Print();
break;

case 83: // CTRL+S
Save();
break;

case 84: // Ctrl+T
DeleteRow(event.srcElement);
break;

//case 82: // CTRL+R
//case 76: // CTRL+L
//case 79: // CTRL+O
//case 87: // CTRL+W
}
event.keyCode=0;
event.returnValue=false;
event.cancelBuble=true;
}

// SHIFT combination
if (event.shiftKey == true)
{
switch(event.keyCode)
{
case 121: // SHIFT+F10
event.returnValue=false;
break;
}
}

// Single keys
switch(event.keyCode)
{
// case 116: // F5
case 122: // F11
event.keyCode=0;
event.returnValue=false;
break;
}

// TAB key
//if((event.keyCode==8 && event.srcElement.type!="text"))
//{
// event.keyCode=0;
// event.returnValue=false;
//}

// ENTER key
//if(event.srcElement.type=="text" || event.srcElement.type=="checkbox" ||
// event.srcElement.type=="radio" )
//{
// if(event.keyCode==13)
// {
// event.keyCode=0;
// event.returnValue=false;
// }
// }

if(!event.ctrlKey && event.keyCode==13)
{
event.keyCode=9;
}
}