This was how I solved mine after 'googling' around...
- Navigate to the directory your node was installed in
- rename your
npm.cmd
andnpm
files - Try run the installation again
- If successful..delete the files you renamed earlier
npm
andnpm.cmd
- if not, :( :(
The cli commands here...in case you don't want to be renaming and stuffs
cd %ProgramFiles%
odejs
ren npm.cmd npm2.cmd
ren npm npm2
npm2 install npm@latest -g
del npm2
del npm2.cmd
Rolf-schmidiger