Bit of a long story so I will try to summarise. PC came with 256m ram. DDR400 PC3200 I bought and exta gig and added into next slot to make 1.25 gig All running well for many years. Then upgraded to a X2 AMD 3800 processor. I think I had reboot with that processor, anyway a month later I got another gig of DDR400 PC3200 I had problems adding that, beeps etc. However eventually I got running with the two 1 gig stick in the first two (of 4) slots. However I was getting reboots, about 1 every 4 hours on average (variable) So I went to just the new 1 gig stick i slot 1. That gave a reboot after 1.5 hours So I tried just the old 1 gig stick in slot one - results -beeps!!! I shifted it to slot 2 on a 'hunch' and it booted up correctly. It has not rebbooted on that yet but I have only been running a couple of hours so not long enough to be conclusive. Something I have noticed is that the first 1 gig stick I got appears to be high density, looking with the Everst utility (below) the module name 128M64K-40C suggests it is arranged as high density. However having said that it had been running fine along side what is a 256m low density module as a (rather badly) 'matched pair' This is the Everest info for the old suspected high density stick. Memory Module Properties: Module Name 128M64K-40C Serial Number 040413C3h Module Size 1024 MB (2 ranks, 4 banks) Module Type Unbuffered Memory Type DDR SDRAM Memory Speed PC3200 (200 MHz) Module Width 64 bit Module Voltage SSTL 2.5 Error Detection Method None Refresh Rate Reduced (7.8 us), Self-Refresh Memory Timings: @ 200 MHz 3.0-3-3-8 (CL-RCD-RP-RAS) @ 166 MHz 2.5-3-3-7 (CL-RCD-RP-RAS) @ 133 MHz 2.0-2-2-6 (CL-RCD-RP-RAS) Memory Module Features: Early RAS# Precharge Not Supported Auto-Precharge Not Supported Precharge All Not Supported Write1/Read Burst Not Supported Buffered Address/Control Inputs Not Supported Registered Address/Control Inputs Not Supported On-Card PLL (Clock) Not Supported Buffered DQMB Inputs Not Supported Registered DQMB Inputs Not Supported Differential Clock Input Supported Redundant Row Address Not Supported Anyway it is all rather confusing. Some questions which occur are 1) Why does the above stick beep in slot one yet run fine (so far) in slot 2? I though I put it in slot one OK, however it is possible slot 1 is 'dirty'. I posted a long rambling thread about it here http://www.techspot.com/vb/topic149949.html Not getting any replies now, not surprising is it is so long and complicated and involved so I though I would try again here and try to summarise it a bit more concisely. I guess I will have to keep investigating and adding info until I can narrow the problem down more, even I am getting confused, I have 3 lots of memoryy from different manufacturers - lol. I don't think it should matter who makes it, however it seems a complex issue.