root dbspace

I have a test machine running Online 7.1. On performing a VERY large query I received an error message saying that there was no free disk space to write sorted rows into a temporary table. On examining the space available in the rootdbs 32252 pages remained out of 575000. I shut down the engine and restarted but the used pages remain the same. How can I release the pages written to by my aborted query?? Tony Reynolds, NEC Group, Birmingham , UK 8-))