Messing around with your clients performance doesnt seem like a nice alternative to a captcha for me... There is plenty of people with bloated windows machines

Messing around with your clients performance doesnt seem like a nice alternative to a captcha for me... There is plenty of people with bloated windows machines that even using a modern browser struggle to perform properly, I dont think overloading them with extra work would help making their experience easy and smooth. Just my 2 cents.