Convert Seconds To HH:MM:SS

Could reorganize to make it a bit shorter, but. . .

//*******************************************************
//Convert seconds to HH:MM:SS
//*******************************************************

function convertHMS(sec)
{

//From JS FAQ by Liorean
Number.prototype.toDecimals=function(n){
n=(isNaN(n))?
2:
n;
var
nT=Math.pow(10,n);
function pad(s){
s=s||'.'
return (s.length>n)?
s:
pad(s+Ɔ');
}
return (isNaN(this))?
this:
(new String(
Math.round(this*nT)/nT
)).replace(/(.d*)?$/,pad);
}
if(sec>59)
{
var hrs=sec/3600;
if(hrs<0)
{
hrs="00";
var min=hrs*60;
min=min.toDecimals(8);
var snd=min.substring(min.indexOf('.'),min.length);
min=min.substring(&#390;',min.indexOf('.'));

if(min<10)
{
min=&#390;'+min
}
snd=Math.round(snd*60);
if(snd<10)
{
snd=&#390;'+snd;
}
var tm=hrs+':'+min+':'+snd;
}
else
{

hrs=hrs.toDecimals(8);
var min=hrs.substring(hrs.indexOf('.'),hrs.length)

hrs=hrs.substring(&#390;',hrs.indexOf('.'));

if(hrs<10)
{
hrs=&#390;'+hrs;
}
min=min*60
min=min.toDecimals(8);
var snd=min.substring(min.indexOf('.'),min.length);
min=min.substring(&#390;',min.indexOf('.'));

if(min<10)
{
min=&#390;'+min
}
snd=Math.round(snd*60);
if(snd<10)
{
snd=&#390;'+snd;
}
var tm=hrs+':'+min+':'+snd;
}
}
else
{
if(sec<10)
{
sec="0"+sec;
}
var tm="00:00:"+sec
}
return tm;
}