Help With 2 Datetime Fields-1 Stores Date, The Other Time

Hi,
We have a lame app that uses 2 datetime(8) fields, 1 stores the date, the
other the time.
example query:

select aud_dt, aud_tm
from orders

results:
aud_dt aud_tm
2006-06-08 00:00:00.000 1900-01-01 12:32:26.287

I'm trying to create a query that give me records from the current date in
the past hour.
Here's a script that gives me todays date but I cannot figure out the time:

select aud_dt, aud_tm, datediff(d,aud_dt,getdate()), datediff(mi, aud_tm,
getdate())
from orders
where (datediff(d,aud_dt,getdate()) = 0)

results:
aud_dt aud_tm
datediff(0=today) timediff (since 1900-01-01)
2006-06-08 00:00:00.000 1900-01-01 12:32:26.287 0
55978689


I added this next part to the above query but it does not work since the
date/time is from 1900-01-01
and (datediff(mi, aud_tm, getdate()) <= 60)


Thanks for any help.