Installing package in windows 7

Hi all,

I was trying to install a package called ei from this 
http://gking.harvard.edu/eiR link . With GCC, r-base-dev and some other R
package dependencies installed it works perfect in my Ubuntu Linux system. 

Now I am trying to install the same in Windows 7 environment. So far my
setup is as follows,

1. R installed in home folder (c:\Users\username\R-2.12.1\R. It is set to
run as administrator, and the R folder is writable.
2. My working directory is (c:\Users\username\Documents)
3. Rtool is installed in (c:\Rtools)

Having this setup, 

4. I tried to install it by the command,
install.packages("ei",repos="http://r.iq.harvard.edu") 
This command gives me the following error message.

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Installing package(s) into ?C:\Users\username\Documents/R/win-library/2.12?
(as ?lib? is unspecified)
Warning message:
In getDependencies(pkgs, dependencies, available, lib) :
  package ?ei? is not available
---------------------------------------------------------------------------------------------------

After that I have decided to have a try to install it from a local zip file,
so I proceeded in the following way,

5. I have downloaded the package ei_0.938.tar.gz, untar it and make a zip
file from that. I placed it into my work directory. 
6. I opened the terminal (Run > cmd), went to the work directory and tried
to run the command R COM INSTALL ei 

---------------------------------------------------------------------------------------------------
It shows me the following error message,
C:\Users\username\Documents>R COM INSTALL ei
'R' is not recognized as an internal or external command,
operable program or batch file.
---------------------------------------------------------------------------------------------------

I am not sure what should I do now. Is there anyone to help?

_ Rdgst.