SharePoint: How can I clean it up, without reinstalling?

Question

I've made a mess of MOSS (well not really, just that I've created some site columns that are now impossible to delete).

Is there any way I can revert to a default installation without reinstalling everything?

Failing that is there a way to force delete site columns?

Update

Basically another "typical day developing around Sharepoint..." moto, with Sharepoint it is 100% probable something will go wrong.

I have Site Columns that can't be deleted, because they're "bound to a content type, that I've already deleted"

Answer 1

1. If you are created custom columns on Document Library level you just need to delete Document Library
2. In case you created custom columns at site collection level you should delete your site collection and create a new one. New site collection will not be affected unless you made some non-supported customizations to "12 hive".

In both cases you can solve the problem without reinstallation.

Hope it helps,