tomoa wrote:

The Asus p2b-F was working good. After i changed memory configuration, i did not put well one of the RAM module in slot and after start, computer hang. I checked it, and I fixed the RAM module by pressing it again. From this time i have problem: pressing ctrl+alt+del hangs computer in bios, dos, windows. ACPI does not work. Button Power off/on does not power off computer even after 5 seconds.

remove the ram from the slot and reboot. if everything is fine, the memory slot is broken.

I reset bios, changed processor, removed memory, problem is the same.

tomoa wrote:

I reset bios, changed processor, removed memory, problem is the same.

Try different PSU.
Don't connect hdd, fdd and odd.
Eliminate the problem by removing 1 part at the time, change the cmos battery. Check default bios settings
Inspect the capacitors.