"cannot find module" when installing npm modules on windows

"cannot find module" when installing npm modules on windows

I am new to NodeJS. I am trying to use npm on Windows 8.
I have installed using chocolatey, cinst nodejs.install (version 0.10.17).
I installed as administrator (and would prefer to run npm as a normal
user).
Node itself seems to be working, I can use the REPL to run simple programs.
If I try to install something using npm, I get cannot find module:
> node npm install express
module.js:340
throw err;
^
Error: Cannot find module 'C:\Users\Klas\Documents\My Dropbox\mina
egna\tech\node\webserver\npm'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:901:3
I have read the answers on Nodejs cannot find installed module on Windows?
but unfortunately it is still unclear to me what I have to do.
I have tried setting NODE_PATH:
In trying to follow this answer, I have tried setting it to
C:\Users\Klas\AppData\Roaming\npm\node_modules (but I had to create both
the npm and the subfolder node_modules myself)
I have tried creating a folder c:\node\node_module (according to this
advice, even though the installation did not even create a c:\node folder)
and setting it to that.
I have tried setting it to C:\Program
Files\nodejs\node_modules\npm\node_modules (which did exist after
installation)
I have also tried to create a node_modules folder below the current
working directory. As I understand it that is where local npm will be
installed?
None of these helped. So it seems to me that setting NODE_PATH is not the
solution?
Using the -g flag makes no difference (I would prefer not to use it).
I get the same error both as normal user and as administrator (I would
prefer to be a normal user).
I get the same error no matter where I execute the command, except when I
do it in C:\Program Files\nodejs, where I get
basedir=`dirname "$0"`
^
SyntaxError: Unexpected token ILLEGAL
at Module._compile (module.js:439:25)