Filtering On Parts Of A Date/time Field

Hi,
I have a date/time field in a SQL2000 database, and what I would like
to do is to filter on a specific part of the field, for example the
time or hour.

Supposing I have a set of data for the last 5 years and would like to
filter out any records which are outside working hours i.e. I would
like to show records where the time is between 9am and 5pm.

Does anyone know if there is a simple way to do this in SQL? If you
simply don't specify the date part in the where clause (e.g. WHERE
issuedatetime between '09:00:00' and '17:00:00') it defaults it to
1900-01-01 so basically no data is returned.
The only way I can see to do this is by using the DATEPART function,
converting it to a varchar, appending 1900-01-01 on to it and
converting it to a datetime, and then using the where clause as stated
above. This is quite a long-winded way, however. Any other suggestions?

Thanks,
Matt