Oracle 11g Express Edition for Windows 64bit?
There is
I used this blog post to install it in my machine: http://luminite.wordpress.com/2012/09/06/installing-oracle-database-xe-11g-on-windows-7-64-bit-machine/
The only thing you have to do is replace a registry value during the installation, I've done it about three times already, and every time found a different reference on-line, none here on stackoverflow.
EDIT: as @kc2001 noted, regedit must be run as Administrator, and added this tutorial: (a bit more colorful): http://www.hanmiaojuan.com/2013/03/install-oracle-xe-11g-for-windows7-64bits.html
I just installed the 32bit 11g R2 Express edition version on 64bit windows, created a new database and performed some queries. Seems to work like it should work! :-) I followed the following easy guide!
Some of more advanced Oracle database features such as session trace do not work properly in Oracle 11g XE 32-bit if installed on Windows 64-bit system. I needed session trace on Windows 7 64-bit.
Apart from that it works well for me in multiple production MS Windows 64-bit systems: Windows Server 2008 R2 and Windows Server 2003 R2.