XMetaL Author Enterprise and XMetaL Author Essential (all versions up to and including 6.0 SP1) are currently only supported on 32-bit versions of Windows XP, Vista and 7.
The next major release of our software (7.0) will officially support Windows 7 64-bit.
For anyone that has issues installing and running our 6.0 and earlier versions on 64-bit machines we recommend "XP Mode", freely available here:
http://www.microsoft.com/windows/virtual-pc/download.aspxWe are supporting this because XP Mode is essentially a 32-bit version of Windows XP (which is supported) running in a virtual machine.
Please see the file "install-readme.html" that ships with the installer as it may contain other information you may need to be aware of.