npm on windows does not recognize installed modules

While npm is working (i'm using recent official build on Windows 7) and modules are getting installed, "npm ls installed" shows empty list, so does "npm ls -g installed" I've tried to set NODE_PATH variable to various paths, that does not seem to work either.

mkdir c:\temp
cd c:\temp
npm install yeti

[...] - everything looks good, yeti is installed

npm ls installed

C:\temp
└── (empty)