Your index is stored in \Solr\core\data
Eg. \Solr\collection1\data
If you delete the data folder or underlying folders “index” and “tlog”, it will delete your index.
A nicer way of achieving this, is by running the following HTTP command
[code]http://localhost:8983/solr/collection1/update?stream.body=<delete><query>*:*</query></delete>[/code]