 This randomized phase II trial studies how well metformin hydrochloride and aspirin work in treating patients with hormone-dependent prostate cancer that has progressed after surgery or radiation therapy. Metformin hydrochloride and aspirin may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. It is not yet known whether giving metformin hydrochloride and aspirin together can slow the growth of prostate cancer. 