Ok, so let me see if I got this straight. You want to take a column that is currently computed and make it a plain-jane data column. Normally this would drop the column but you want to keep the data in the column.
- Make a new table with the primary key columns from your source table and the generated column.
- Copy the data from your source table into the new table.
- Change the column on your source table.
- Copy the data back.
No matter what you do I am pretty sure changing the column will drop it. This way is a bit more complex but not that bad and it saves your data.
[Edit: @SqlMenace's answer is much easier. :) Curse you Menace!! :)]