I registered on http://Oracle.com in order to download 11g R2 Express edition database. But http://Oracle.com offered me download links only for Windows 32bit and for Linux 64bit.
Is there somewhere 64bit Windows version of Oracle 11g XE database? Are 64bit versions available only for paid Oracle db?
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