I didn't installed any new hardware or even any new software. System was working perfectly until the point when the error occured.
Not even an another hard disk with a fresh instalation of win xp from win xp cd or from my previous ghost image works. It always reports the same error.
My mainboard is Asus K8N4-E Deluxe (AMD Sempron 2800+, 2X512 MB DDR 400 Mhz RAM, Radeon X550 256 MB, 200 GB Maxtor)
I never tammper with BIOS, in other words, MBO has it's original BIOS.