I wasn’t able to locate installer_nodejs_windows.msi on my PC, so I downloaded it separately from here: http://go.aptana.com/installer_nodejs_windows
After installing Node JS for Windows, I was able to successfully install Aptana.
Note: Above link no longer seems to be working. Looks like you can download Node JS separately from here: https://nodejs.org/download/release/v0.10.13/