This seems to be a first run issue.
I downloaded 0.6.3 today, ran it, used download.bat to update, then used install.bat to install. (Used C:\gnuwin32 as the install path). After the supplemental install completed, install.exe and install-info.exe were both just empty files (inside the gnuwin32\bin directory), which lead to errors when install.bat tried to use install-info.exe. I deleted install.exe and install-info.exe and ran install.bat again and it ran correctly that time.
Using Windows XP Pro x64.