Zenwalk is based on Slackware. It tries to be a complete, modern and user-friendly operating system that is very fast so it can also be used on older systems.
Zenwalk uses Xfce 4.8.1 as desktop environment (other versions of Zenwalk with other DE's are available too) with Linux 2.6.37 as kernel. The ISO-download is 583 MB big
Installation
The installer is ncursed based, but the option 'Autoinstall' makes it very easy. The installer is split into two: the first part partitions the disk and installs the packages, the second part creates the accounts (user and root) and localizes the installation. Remarkable fact is that Zenwalk still used Lilo as default (and only) bootloader. As far as I am aware of this is the only distribution that doesn't use Grub. Not that this is a real problem, it's just something unusual.

First Impression
Boottime: 32s
Memory Usage: 99,01 MB
By default Zenwalk installs a couple of applications which should be enough to get you on the road:
- LibreOffice 3.3.1 as Officepacket, not really lightweight
- Icecat browser, a fork of Firefox
- Icedove Mailing program, a fork of Thunderbird
- The Gimp; opensource Photoshop-clone
- Pidgin
- Transmission BitTorrent client
- Totem media player
One strange thing happened when I tried to run a movie or MP3-file: Totem just did not wanted to start. In Terminal I got a bunch of error messages. but the application didn't start. When I selected a mirror in Netpkg, Totem suddenly started (I'm not sure if this is coincidence or not), now it starts everytime. Anyway once Totem I had no problems playing any file I wanted to play.
Netpkg, the package management system of Zenwalk does its job; bot nothing more than that. It's not very clear in comparison to for example Synaptic and I found it rather to be slow responding. I noticed that some of the repositories are for the current release 7, but some are from the previous (Zenwalk 6.4). This mix of repositories is confusing, is it ok to load 'old' packages on a new system?

Conclusion
Zenwalk is indeed pretty easy on resources, however I did not always had the feeling of it being responsive. Most tools you need are there although there's no real consistency between the desktop/applications. I would like to see the original applications as Firefox and Thunderbird.