Vostro 220, hangs on reboot

Hello everyone, i'm new to this forum. I have upgraded my Dell Vostro 220 from an E8300 cpu to a Q9550, after updating the bios to V1.3.0 that is the latest version. I've choosed Q9550 following this thread: https://www.dell.com/community/Desktops-General-Read-Only/Upgrading-a-Vostro-220-from-a-E8400-to-a-Q9650/td-p/3369656 Everything seemed ok, i have stress testes the cpu and the ram and tested it for some hours, and it's much faster and pleasant to use than before. But i have a problem. If i reboot the pc, from Linux (Ubuntu 16.04 64 bit) and even Windows XP 32 bit, it hangs on reboot. Turning it off and restarting works fine. Help appreciated. Thank you in advance.