Archive files in both Windows and Linux using PeaZip
If you need an archiving program that can run under both Windows and Linux, sport a graphical interface, and be licensed as open source software, only a single program will do: PeaZip.
It acts as a graphical front end for several tools that provide archiving, compression, encryption, and similar functions.
The Linux version of PeaZip is desktop-neutral, which means you can use it no matter whether you prefer KDE, GNOME, Xfce, or another desktop or window manager. The integration with the desktop might not work in all cases, because it depends on freedesktop.org standards; however, the basic functionality won't be affected. The software doesn't require special installation; simply plop it in any path (it will work even from a USB memory stick) and you'll be able to start using it.
The PeaZip download site
contains the Windows version and several Linux options: a
Portable/Standalone version with which you'll have to perform several
extra installation steps, and prepackaged versions (deb and RPM) that
are easier to install. Being an openSUSE user, I chose the RPM one.
After downloading it (it's only about 5.5MB), type rpm -Uvh peazip_theVersionYouDownloaded.rpm as root, and the program should install and integrate with your desktop.
If you prefer doing the installation yourself, get the Portable/Standalone version. After the download is complete, go to wherever you downloaded the package, and enter these commands as root:

