In my windows installation
Everything you need is to read
npm-folders documentation. I don't want to start my Win notebook now so I cannot verify it, but you should only change
c:\Program Files\nodejs in your config file. If you want to change it globally for all users, edit
c:\Program Files\nodejs\npmrc file, otherwise create/edit
But this change will have probably some side efects so read this discussion before. I think your idea is not a good one.