A system for testing a memory page of a computer while an operating system is active. The system includes a hook function and a pattern generator. The hook function has software instructions that takes the place of a memory allocation/release scheme of the operating system. The system stores a test pattern generated by the pattern generator in the memory page upon receiving a request to release the memory page. Upon receiving a request to allocate the memory page, the system verifies the test pattern is correct to ensure the memory page is not defective. If the test pattern is incorrect, the defective memory page is removed from service.