Changing the size of a Varchar Field

We have a small table of about 13 million rows that needs altered. A column in the table needs to be changed from a varchar(20) to a varchar(500). When we ran the alter table script, 3 hrs later and it wasn't done running. Any suggestions on what we can do to speed up the process?

Thanks ahead of time
DMW

Edit:
We are running SQL Server 2000 and the db at the time was running in simple moodBulk copy it out, redefine the table without indexes (except clustered or primary key) or triggers, bulk copy back in with a batchsize set to keep the log from growing too large, reapply the indexes and repost the triggers.sql