You can not directly install testrpc on windows. But you can install it using Chocolatey.
Refer to this site to install Chocolatey: https://chocolatey.org/install
After installing it, Open command prompt as administrator and run the following command to install pre-requisites.
$ choco install nodejs.install –y
$ choco install git –y
$ choco install VisualStudioCode -y
To install testrpc, run the following command:
$ npm install -g npm
$ npm install -g -production windows-build-tools
$ npm install -g ethereumjs-testrpc