Most "key generators" or "cracks" are bundled with malicious code that can steal your personal data.
For many years, this has been the go-to free alternative. SageThumbs is a powerful shell extension that allows Windows to display thumbnails for a massive range of formats, including PSD. It is open-source, free, and generally lighter on system resources than older commercial codecs. ardfry psd codec 17 00 key link