Error Installing on Windows About the PATH Not Updated
While installing Salesforce CLI on Windows using the *.exe installer executable, you get the error PATH not
updated, original length XX > 1024, where XX is
a number greater than 1024.
The error looks something like this:

The problem is that your PATH environment variable has a value whose string length is greater than 1024. This limitation isn’t from Salesforce CLI; rather, it’s a limitation of the Nullsoft Scriptable Install System (NSIS), which Salesforce CLI uses for its Windows installer. The installer is checking for the PATH length on your computer to make sure that NSIS fails gracefully and doesn't get into a bad state.
To fix the problem, manually update your PATH variable to be shorter, such as removing unneeded paths. Check your Windows documentation for details.