Insert statement taking enoromous amount of time

Hi

Yesterday night I tried to fix some data to our production Sever. I have run a script which actually insert 178000 rows into a table. my script is like:

insert into table1 select *from table2;

in table2 already 178000 data exists and I was tried to insert those data into table1. But the whole script was taken more than 2 hours and not finished and at alst I have cancelled this.Please advise me the ebst solution to insert or update enoromous data into table.

Thanks

Mukit