The vast majority of websites offering "Microsoft Toolkit v2.6.4 free download" are scam sites. According to antivirus vendors (Kaspersky, Bitdefender, Malwarebytes), many MTK files are bundled with:

While the technical capability of Microsoft Toolkit v2.6.4 to activate software is proven, the risks vastly outweigh the benefits. You are trading a one-time payment for the long-term security of your personal data, files, and privacy. The internet is flooded with infected versions of this file, and even the “clean” version is illegal and unsupported.

The latest version of Microsoft Toolkit, .v2.6.4, comes with several new features and improvements, including: