R CMD on Windows 7 Error - "R" is not recognized as an internal or external command,

• Have you closed the command prompt and opened a new one after adjusting the PATH?
• Enter the command PATH on the command line and ensure that you are properly updating your path
• Try navigating to the directory where R.exe is saved and running it locally -- cd C:\Program...\bin\x64, R.exe.
• Ensure that you're running on Windows' Command Prompt and not Cygwin's terminal
• If you actually have a space after the semi-colon in your PATH, you'll need to remove that: /bin;C:/Program.... Try combining that with Joshua's solution.

I attach my whole solution here:

1. Install Rtools which is compatible with my R version
2. Add PATH: C:\Program Files\R\R-2.15.1\bin\x64;C:\Rtools\bin;C:\Rtools\gcc-4.6.3\bin
3. In cmd, enter: R CMD INSTALL packagename

Click "enter", done.

I had a lot of trouble getting this to work, and finally found the golden nugget on r-project (R doesn't like spaces in paths) so here's how I finally did all this:

• I installed R to "c:\programs" instead of "c:\program files...". My final path to RSCRIPT.exe is "C:\Programs\R\R-2.15.2\bin\Rscript.exe"
  • I added that directory to my PATH, but that doesn't seem to help
  • RStudio is also installed under c:\Programs (e.g. c:\Programs\RStudio), but RTools is installed under the "c:\" root directory (e.g. c:\RTools).
• I downloaded all the packages to "c:\downloads\r"
• I opened a command prompt in "c:\downloads\r" and ran the R CMD install from this downloads directory, specifying the path to R
  • e.g. "C:\Programs\R\R-2.15.2\bin\x64\R CMD INSTALL colorspace_1.2-0.zip"