This was discussed in several other threads and think it deserves its own subject.
I claim that the CPA test changes every window. Some say it is the same.
15% of the questions and one SIM are "pre-test" (per the AICPA):
"Responses to pretest questions are never taken into account in calculating candidate scores. Pretest questions are included in every Examination (they may be multiple-choice questions, task-based simulations, or written communication tasks) only for the purpose of collecting data. The data are needed to assess the quality of the questions, and to collect scoring information for later use when the questions become operational items."
Furthermore, the AICPA has hundereds of SIMS in its bank and it increases 15% with every test. As such it is virtually impossible to receive the same questions on subsequent windows. This has been confirmed by posts on A71 where members who took the test "gazillion" times never encountered the same SIMS.
I think that if you spend 2 hours working on a SIM you would remember it. Especially if you blame it for failing you.
The situation changes if you take the test within the same window, where the subset of questions is much smaller. Then you have a much higher chance of seeing the same SIM, thus retaking tests within the same window is not allowed.