Node.js Module Install Not Working

I have successfully installed node.js(v0.10.29-x86) on my windows machine(32-bit) and able to run 'hello world' program. Now I need 'express' module to be installed. I tried using

npm install express

and

npm install -g express

without any success. I get following error in command line whenever I run my js file.

module.js:340
throw err;
      ^
    Error: Cannot find module 'express'

    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (D:\node\test.js:1:77)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.runMain (module.js:497:10)

Please help.