Windows 7 reached end‑of‑support on January 14 2020. Installing .NET 4.8 is still possible, but no security updates will be provided for the OS itself.
用於Windows 的Microsoft .NET Framework 4.8 離線安裝程式 microsoft net framework 4.8 32 bit windows 7
. While it is installable, please note that Microsoft has ended official support for Windows 7, which may impact security and future updates. Essential Requirements for Windows 7 Windows 7 reached end‑of‑support on January 14 2020
Below that: Download and install.