Driver irql not less or equal BSOD

[GengisKum]

Ok guys, help me figure out this mess.
Fresh install of windows xp sp2 pro, drivers up to date (checked on driveragent.com), no irq conflicts.
I get a driver irql not less or equal crash on the PCI Sata controller driver sil3112.sys and random STOP errors.
Memtest reported no problem. No virus on the computer.
What can I do?

EDIT: hardware is: MSI KT3 Ultra2 mobo (VIA KT333 Chipset and VIA VT8235 Chipset and AC97) cpu amd athlon 1200, external SATA PCI controller Silicon Image 3112, Ati radeon 9250 agp, 384 mb ram, 120gb western digital sata drive and liteon 832s dvdrw.