Just a suggestion ...
That A21M is quite an older laptop with a Pentium 3 processor. As such, even with 512 MB RAM, KDE 4 is going to run quite slowly on that computer. Perhaps you would get better performance using one of the lighter desktops under PCLinuxOS. I can heartily recommend PCLinuxOS Phoenix, PCLinuxOS-LXDE, and PCLinuxOS-e17. Any of those versions of PCLinuxOS are going to run MUCH faster on that older computer. KDE 4 is better suited for more modern machines.
FWIW, I also have an A21M with 512 MB RAM, so I can attest to the speed increase, first hand.