Mandriva defaults to the KDE desktop, but many other environments are included (xfce, black box, IceWM-lite, etc.) and you can choose the one you like best. Many of the desktop environments are light on resources so Mandriva may do very well on a vintage computer using them.
Alternatively, if you want a distribution designed for use on a vintage computer, you may want to try Pupy Linux
. Both have a good reputation for stability and are actively supported.