Any help on my following problem would be much appreciated.
My PC, an Intel Celeron X86 Family 6 Model 8 Processor 797 MHz originally had Milenium ME operating system which I have upgraded to Windows XP Pro Version 2002 Service Pack 2.
I have also doubled the memory to 512mb by adding a Crucial 256mb PC133 stick to the original crucial PC133u 133 MHz stick. Both sticks are CL 2 and non parity and non ECC and 256 mb which I have confirmed as correct with the crucial memory tester and through Compaq.
Since adding the new memory it freezes very regularly within minutes). It freezes very rarely when I try just the 1 stick of 256 mb ( be it with the original or just the new one).
For each 'freeze', the Event Viewer in the 'system' folder with the source 'acpi' shows the error in the Title box.
When opening up the error it shows:
AMLI: ACPI BIOS is attempting to read from an illegal IO port address (0x75), which lies in the 0x74 - 0x76 protected address range. This could lead to system instability
I have checked the BIOS and it is fully up to date.

Thanks in anticipation

Just a quick update. The PC is a Compaq

if the pc starts up then what you can try is to run memtest on the pc,this will tell you if the memory is working correctly or not and it will tell you if its compatible with the system!

Thank you Loki, I have run memtest86+ with the memory and it passes the tests ok

Thank you Suspichio for your link. My BIOS is up to date and the memory has been tested ok with memtest86+. I must admit that I didn't really follow what to do when reading the other suggestions in the link you suggested. It's odd as I tested the 512 mb memory with memtest last nigh and it said it was fine. I then started up the PC, went into the internet for a few minutes which was fine and then I attempted to open Contol Panel and it froze. I am about at the point of giving up and running it just on 256 mb memory which seems fine