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If you deleted only the folder and had not uninstalled prior, all the info should already be in the DB, and would not required install. The message you are getting is, in fact, a message telling you the tables already exist.
Technically, I think everything should work the same as prior deleting the folder. Of course this is taking for granted that you hadn't modified the DB at the same time.
I've tested on my local machine and if you just delete and then recopy the folder in modules nothing has changed and everything will work fine, not needind install.
Cheers
Note: If you uninstall the module you will wipe out the tables and all forums posts.