What are the system requirements to run –bgopacity option in a windows machine?

I’ve tried adding to option (--bgopacity) to the startup command but I can not get a transparent background

I’m using Chimera 2.2199

Thanks!

Roberto

Roberto Vanacore, PhD

B-3101 Medical Center North

Vanderbilt University Medical Center

1161 Twenty-first Ave South

Nashville, TN 37232-2372

Phone: 615-322-7306

Fax: 615-322-7381