The following works on 2008R2+ to produce 'HH:MM':
select
case
when len(replace(replace(replace(right(cast(getdate() as varchar),7),'AM',''),'PM',''),' ','')) = 4
then '0'+ replace(replace(replace(right(cast(getdate() as varchar),7),'AM',''),'PM',''),' ','')
else replace(replace(replace(right(cast(getdate() as varchar),7),'AM',''),'PM',''),' ','') end as [Time]