Help With Partitioning And Between

I have begun my quest to become familiar with SQL 2000 table partitioning and have had some success.
I've partitioned tables according to the "rules" and guidlines of other papers and the show plans look good for all cases.

But when I went to create another demo series, I got stuck.
I've created two tables, with the appropriate CHECK constraints, and with a "union all" view.
When inserting data, it goes to the right tables.
When reading data with a where clause like:
col1=10,
the show plan shows the query getting the data from the ONE correct table.
BUT
When the where clause looks like:
where col1 between 1 and 10:
the showplan shows the query getting data from both tables, instead of the table that 1 to 10 belongs to.
Help!