Final answer:
Lenovo Vantage has replaced Lenovo Solution Center as the preloaded tool for Lenovo PC diagnostics, offering a user-friendly interface and comprehensive system management features.
Step-by-step explanation:
The tool that has replaced Lenovo Solution Center as the preloaded tool for Lenovo PC diagnostics is Lenovo Vantage. Lenovo Vantage provides system updates, hardware scans, and the ability to manage update settings, among other features.
It's designed to provide a more user-friendly interface and a comprehensive suite of services that were traditionally spread across different applications such as the Lenovo Solution Center, Lenovo System Update, and Lenovo Companion.