when I click "install" for 2checkout, I get error message

[RodG]

It's VERY DANGEROUS for me to tell you this, because this will DELETE any data already in the table, which means it could delete important history if you've been using the module previously. So, YOU HAVE BEEN WARNED.

If the error says "Fatal error: 1050:Table '2checkout' already exists " then the tablename is "2checkout", so you would go into phpMyAdmin, find the table named "2checkout" and check the box next to it, and choose "drop" from the menu. Or you could click the "SQL" tab and type "DROP TABLE 2checkout;" and click Go. The table will be instantly gone, WITH NO WAY TO GET ITS DATA BACK.
Then you can proceed with installing the module again.

FWIW, if/when I'm ever in this situation I'll *never* delete the table. I simply rename it. This way, after the install script has done its job without error it is usually a matter of copying the data from the renamed table to the newly created table (assuming that there is data that needs to be recovered).

This method also avoids the need for MC12345678's suggestion to edit any scripts to 'skip' the line that is trying to insert the duplicate table... AND it allows comparison between the old and new table structures for any differences.
Just my 2cents worth.

Cheers
RodG