What happens when I drop a clustered primary key in SQL 2005

Question

I've a PK constraint - a clustered index on two columns - which I am in the process of dropping. The command is still running after an hour. I would have thought that as I am just removing a constraint the operation would be nearly instantaneous. Can someone explain to me what is actually happening under the hood when I drop the PK?

Answer 1

Clustered index is not "just a constraint", it's a storage method.

When you drop it, your data are being reordered from clustered storage to heap storage

Other indexes are being updated to refer to RID's instead of PRIMARY KEY values.

Answer 2

The clustered index is the data, that would explain the time it is taking to run.