Versions 3.x and 4.x may play, older versions...may hijack the thread. ;)
What is the most minimal-resource computer system you've been able to run "pure" KDE -- pure as in no apps from any other desktop enviroment, not necessarily pure as in compiled-from-source.
My starting bar:
KDE 4.2 on a AMD 5000+ 64-bit dual-core, 1 GB PC3200, 250GB SATA hd. Ext2 & Ext3 filesystems.
Memory usage as measured by conky: ~405 MB RAM