On the openSUSE web page are downloads for installable liveCDs for both KDE and Gnome (and for 32-bit and 64-bit - although since you mention old PCs I assume you want 32-bit).
… also , if you are not a strong Gnome nor a KDE user, and if these PCs are really really old, you could also look at LXDE or SOAD (Enlightenment) desktops using community CDs. Take a look at:
You may find installation a bit tricky, as that is where a lot of memory can be used. But typically, there are work arounds. One way is in the initial green menu is to select F3 and choose a text boot. This will boot to run level 3 (ie a terminal/text login with networking), and then login in as “linux” (passworld is <enter> for LXDE and password is “soad” for SOAD) and when in run level 3 type ‘su’ to get root (again password will be <enter> for LXDE and again password will be “soad” (no quotes) for SOAD) and then run yast, and under misc choose the installation option in YaST.
The LXDE liveCD is for openSUSE-11.1 as the openSUSE community have not yet created an 11.2 version (although an 11.2 version is being tested).
The SOAD (Enlightenment) version is for 11.2.
There is a wiki page here which keeps track of the openSUSE liveCDs: Live CD - openSUSE.