Converting a datetime to hh:mm:ss format

I'm am tracking employees individual job times. I'm given there beginning time and their ending time in 2 columns both datetime format. I worked out an ugly DATEDIFF to give me individual components but it's not completely usable.
I have been struggling with this issue of how to convert a datatime to hh:mm:ss. If the amount of time it took the employee was 1 hour, 8 minutes, and 9 seconds I don't want to see 1:8:9, I want to see 01:08:09.
*Side note: My server is 2008 R2 and the server I'm querying is 2008 R1 which is causing "Invalid Column Name" errors, but our company has locked out being able to use the Microsoft Update page which is really annoying considering it's necessity in circumstances such as these where I need that update.
TIA

This is the uglier version. I'm currently updating with the hotfixes to my SQL Server or I would give you the current which still is not working.
I'm not presenting a front-end at this time. I'm just gathering some raw data from our db.
I apologize for the coloring I had to copy this out of an email. The yellow highlighted fields from the db and the green is what I'm getting "Invalid column names" errors with. Hopefully these updates will resolve that part at least.
This is the format the last 3 "INDICATED" fields are in: 2011-02-16 11:31:26.000SELECT [IDDPORDERNUM] ,[ORDERTYPE] ,[EN_ROUTE_INDICATED] ,[ON_SITE_INDICATED] ,[ENDED_INDICATED] ,[WORKED_HOURS] = CASE WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600))) = 1 THEN '0' + STR((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600))) + ':' WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600))) = 2 THEN STR((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600))) + ':' END ,[WORKED_MINUTES] = CASE WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600)*60) = 1 THEN '0' + STR(FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600)*60) + ':' WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600)*60) = 2 THEN STR((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/3600)*60)) + ':' END ,[WORKED_SECONDS] = CASE WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED]))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)*60)) = 1 THEN '0' + STR((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED]))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)*60)) WHEN LEN((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED]))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)*60)) = 2 THEN STR((FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED]))- FLOOR(DATEDIFF(ss,[ON_SITE_INDICATED],[ENDED_INDICATED])/60)*60)) END ,[WORKED_TIME] = [WORKED_HOURS] + [WORKED_MINUTES] + [WORKED_SECONDS]FROM [<catalog>].[dbo].[<table>]WHERE CONVERT(DATE,[ENDED_INDICATED] ,113) BETWEEN '2011-01-22' AND '2011-02-21'

<P mce_keep="true">[quote user="FrankKalis"] <P>You might hide some of the ugliness by using a function called via CROSS APPLY. <IMG alt=Smile src="http://sql-server-performance.com/Community/emoticons/emotion-1.gif"></P><P>[/quote]</P><P>&nbsp;When I was referring to the "ugliness" I meant how the layout&nbsp;pasted in, but I looked up CROSS APPLY, as you said it, and I definitely like that much more than using a join.&nbsp; Many thanks to you on mentioning that function!!</P>

A shorter version (ran fine on sql2k8 R1 & R2):
'worked_time'=convert(varchar(8),cast(datediff(ss,ON_SITE_INDICATED,ENDED_INDICATED)/86400.0 as datetime),14)

lol - Frank is a faster typist than I. I might delete my posts...

Thanks guys! This has helped me out A LOT.

Well I found an issue that I didn't state would be needed previously.
I'm also trying to total the time each employee spent on their individual jobs through the course of a month and of course the following gave me an error. How could I resolve this?
I'm going through a different table now hence StartTime and StopTime replace ON_SITE_INDICATED and ENDED_INDICATED respectively. They both have the same datetime format however so this changes nothing.,
SUM(CONVERT(varchar(8),CAST(DATEDIFF(ss,i.StartTime,i.StopTime)/86400.0 as datetime),14)) as Total_Worked_Time

here is *hh:mm:ss (* for hrs beyond 99)
Test code:
DECLARE @s datetime='20110401', @e datetime='20110407 18:30:10'
SELECT
'total_worked_time'=
CASE WHEN (CAST(@e as float)-CAST(@s as float))>1.0 THEN
cast(floor((CAST(@e as float)-CAST(@s as float))*24.0) as varchar)+
substring(convert(varchar(8),cast( ((cast(@e as float)-CAST(@s as float))-FLOOR((cast(@e as float)-CAST(@s as float)))) as datetime),14),3,6)
ELSE
convert(varchar(8),cast( ((cast(@e as float)-CAST(@s as float))-FLOOR((cast(@e as float)-CAST(@s as float)))) as datetime),14)
END
Your code (basically replace datediff - substraction with your columns and add sum for aggregate)

SELECT
'total_worked_time'=
CASE WHEN sum(CAST(i.stoptime as float)-CAST(i.starttime as float))>1.0 THEN
cast(floor(sum(CAST(i.stoptime as float)-CAST(i.starttime as float))*24.0) as varchar)+
substring(convert(varchar(8),cast( (sum(cast(i.stoptime as float)-CAST(i.starttime as float))-FLOOR(sum(cast(i.stoptime as float)-CAST(i.starttime as float)))) as datetime),14),3,6)
ELSE
convert(varchar(8),cast( (sum(cast(i.stoptime as float)-CAST(i.starttime as float))-FLOOR(sum(cast(i.stoptime as float)-CAST(i.starttime as float)))) as datetime),14)
END

You could use patindex to elim case -> it's your fun... now I've to get back to work & worry!

Wow... That totally went over my skill level.

Yes and thank you. This is a great forum!