Prolonged Execution For Table UPDATE Statement - Not Sure It Finishes

I am cleaning up a large database table that has Date keys instead of real DateTimes. To do this, I am running the following query...

UPDATE MQIC.DBO.OBSERVATION_F

SET MQIC.DBO.OBSERVATION_F.OBS_DATE = MQIC.DBO.DATE_D.ACTUAL_DATE

FROM MQIC.DBO.OBSERVATION_F INNER JOIN MQIC.DBO.DATE_D

ON MQIC.DBO.OBSERVATION_F.DATE_KEY = MQIC.DBO.DATE_D.DATE_KEY

where Actual_Date is what is being stored, and the Date_Key is to be dropped.



The particulars are this -

Date_D table - 92,000 rows - 40 MB

Observation_F - 2,000,000 rows - 3.2 GB

This is being run on a remotedly hosted rack server with an AMD processor, 1 GB RAM, 60 GB harddisk space, 20 GB used.



SQL-Server 2005 Express - SP1



If I do the same query as a SELECT Statement,



UPDATE MQIC.DBO.OBSERVATION_F

SELECT MQIC.DBO.OBSERVATION_F.DATE_KEY, MQIC.DBO.DATE_D.ACTUAL_DATE

FROM MQIC.DBO.OBSERVATION_F INNER JOIN MQIC.DBO.DATE_D

ON MQIC.DBO.OBSERVATION_F.DATE_KEY = MQIC.DBO.DATE_D.DATE_KEY

it runs to completion in about 15 min - during the entire time there is extensive used of CPU from Task Manager.

If I do the above statement, it seems to use lots of resources (50% +) for about 5 min, then falls to 5%. It just seems to sit there, for an hour + at which time I've killed the query.

This is actually the second time I tried this. The first time was on a different machine, with the P4, 3GB RAM, plenty of disk space, and using SQL-Server 2005 Standard - SP1. Exactly the same decrease in resources happened, and even though it ran several hours, no results.

Any thoughts here - not waiting long enough, memory leaks, etc.?

Thanks!