If your goal is to type on WhatsApp using a physical keyboard similar to classic HTC designs, several modern Android-powered options support the current official version of WhatsApp:
What (games, tools, utilities) are you hoping to find for it? whatsapp messengercab for htc windows mobile 61 free
Released in 2008, Windows Mobile 6.1 powered classic HTC smartphones like the Touch Pro, Touch Diamond, and HD1. Because this operating system predates the modern application ecosystems of iOS and Android, software installation requires manually transferring a CAB file to the device storage and running it via the built-in File Explorer. Step-by-Step Installation Guide for HTC Devices If your goal is to type on WhatsApp