Yep, that pretty much has been my experience so far too.
I thought the same thing, let's uninstall this bad boy. First thing I want to tell you is that I hope you installed OBIEE 11g to your root directory (i.e. C:\ ). If you buried the install deep in a folder structure, you may have issues deleting files.
Here's roughly the steps that I took:
1) Uninstall OBIEE. --Sounds like you completed this.
2) Noticed weblogic components did not get uninstalled. Went to start menu, weblogic ->Uninstall. Uninstalled those components. -- You still need to do this.
3) Tried to delete remaining files in OBIEE 11g folder for clean re-install. Got error message saying file was in use. Go to your Windows Services (you're on Windows right?) and kill any running Oracle OBIEE 11g services that weren't taken care of by the uninstall process.
4) Delete the remaining files. If you did put your install too deep in a file structure, you'll have to get creative about how to remove the deepest files.
Good question. You definitely don't need to drop the database itself. You can probably just drop the users or re-run the RCU and make new users.
To be completely honest, I didn't do anything with the DB. I took the lazy approach and left it in what ever state it was. I was curious to see if it would error out when I re-ran the install. In hind-sight, I should really have dropped the user/tablespace created with the cascade option.
This error means that your java have problem please install the same version of java some other drive on the server and copy that java newly installed files and past it your existing folder path then try to uninstall it again.
Finally I uniistalled and re installed again but under instance->instace1 folder is renamed to instance2 and next time i installl it renamed to instance3...I thought it would be because of service OPMN with intance1 and next time i installed it srated OPMN instance2 service . I deleted the services from regisrty but it installed with instance3 subfolder and OPMN instace3 service name and older services are still existing even though I delete it from regisrty entriies....