CPU Fan Error M3A78EM and more great problems

Hello,
I have a PC with M3A78-EM mother. Few days ago, I have changed from Sempron 3000 to Phenom X4 920 and 2 GB memory 800 MHz (Kingston). It appears a message CPU Fan error, but fan is working. Simultaneously, Windows xp goes to disapears (in 5 days, first requiring restore point, today dont appears in GRUB). Ubuntu is working OK, but disk C (system) is unreadable. ¿May be a problem of BIOS? ¿Can you help me? Thank you, excuse my English, please