So, seeking for the simplest setup possible (no 3D gaming / video editing / heavy simulations on this PC), I purchased an Abit NF7 board (nForce2, USB2, built in sound and LAN) and the AMD Sempron 2200. Additionally, I got me a good CPU fan (Thermaltake) and a new power supply (since the old one didn't provide the 12V the board needs).
All in all 870 NIS (~$190), not too much.
One pain in the arse though is Windows XP that didn't agree to run after the board/CPU upgrade, which is (they say...) typical for XP. So, I had to reinstall it (took 30 minutes, the CPU is pretty fast). Unfortunately, I'll have to reinstall it again, on another HD because I want to restructure my HDs/partitions. So, I'll take Partition Magic to separate a 20 GB partition for WinXP from my monster 120GB HD and install it there. Hopefully it all won't take much longer.