Morteza,
Due to technical constraints, the 64-bit version of MyEclipse on Windows does not currently include the REST Explorer. You can install a 32-bit version of MyEclipse, even on 64-bit systems to get the REST Explorer working.
When running the installer, it will prompt you to select 32 bit or 64 bit install.Choose 32 bit instead of 64 bit.
Let us know how it works for you.