here are the listed requirements for KDE install
Modern Intel or AMD processor.
Memory & storage
RAM : 512 MB minimum, 1 GB recommended.
Hard disk : 3 GB minimum, 10 GB ore more recommended if you plan to install additional software from our repository.
nVidia, ATI, Intel, SiS, Matrox, VIA.
3D desktop support requires a 3D instructions set compatible card.
Any Sound Blaster, AC97 or HDA compatible card.
CD/DVD drive required
my guess would be that 512MB on a shared memory machine would not be quite enough.