If you are looking for a way to actually use WinCC 7.5 without spending thousands of dollars upfront, there is a legitimate path that won't wreck your computer: Siemens Trial Version : Siemens offers Trial DVD/Downloads
Best for short-term evaluation or learning a specific feature quickly. Wincc 7.5 Download Free
Siemens provides a of WinCC 7.5 directly from their official website. If you are looking for a way to actually use WinCC 7
For those ready to try the official 30-day trial, follow this guide. follow this guide.