Vista recognizes only one core after tinkering with ACPI driver (Standby didn't work...however...). In Device Manager under Computer it says ACPI-PC, not ACPI Multiprocessor-PC or ACPI x86-based PC... With this ACPI driver Windows is not able to handle multiple cores. When trying to update the driver it doesn't show up the other drivers....however it shows up right in bios setup and it is up to date .

First thing I'd check is that the Bios is up to date.

of course it is

Checked some more - I don't know what you did to get the driver you have, but it appears you have installed/selected the wrong one. What I haven't found is details on how to reverse the process.

So let's check the system files, and see does that fix it:

In the search box type cmd, then right click the cmd link and select 'Run As Administrator'. Doing it this way starts you with elevated permissions...

Now you have the command screen - type sfc / scannow

This should check the system files and repir them as necessary. After running this command, you may as well head off to the kitchen to make a snack and maybe watch some TV or something. It can take a while.

I dont think the problem is from the system files bec. this is a fresh install and i have reinstalled windows three times in hope to fix it but i does not.
although i did what you said but it does not do any thing>>>and remeber all my problem is changing the computer type from (acpi) to (acpi x86 based pc).

I didn't find one for Vista... But here's a KB for XP and Server:

http://support.microsoft.com/?id=309283


Key phrase: "Microsoft doesn't support going from "Advanced Configuration and Power Interface (ACPI) PC" to the multiprocessor HAL"


The solution is to repair your installation: http://www.vistax64.com/tutorials/ [...] vista.html

As i said before the problem is not from the windows installion ,as i am working on a fresh install and reinstall windows three times.it is a hal problem!!!!!!!!!