Which indexes to drop

Hi,

I'm optimising my data load by dropping indexes.

My question is, what do I do with the indexes created by postgres for primary keys ?

Is it OK to drop them ?
What will happen to the constraint checking ?

How do I create them again afterwards, so that they are used correctly for constraint checking ?

Say I have a table:

create table transmission (
id serial not null,
start timestamp not null default CURRENT_TIMESTAMP,
stop timestamp,
complete boolean not null default false,
primary key(id,complete)
)

This will have an index:
transmission_pkey

After data loading can I create it again as follows ?

CREATE INDEX transmission_pkey ON transmission(id,complete)

Thanks
JohnT