Gigabyte Mainboard GA 845PE 667 Pro. I built this PC using 256 MB PC 2700 DDRRAM Matrix brand using Samsung DIMMS The PC has been fast and stable. I have not tried overclocking. I have tried to upgrade the RAM with another 256 MB to give a total of 512MB. But got system reboots instead. I tried in slots 2 and 3 - no luck. I now have some RAM same as the original but a different batch. However, this has also given system freezes and reboots. I have tried this DIMM in slot 1 – no problems. Add in the original DIMM into slot 2 or 3 gives reboots and freezes even when no applications are running. System details Win XP Professional Version 2002 SP1. BIOS Award 08/29/2002-I845PE-6A69YG03C-00, now updated to BIOS Award 10/16/2002-I845PE-6A69YG03C-00 CPU ID: 0F24 Patch ID: 000B7 Video card Leadtek Winfast A170T GEForce4MX 440 with 64MB DDRRAM, BIOS Ver 4.17.00.45, Driver nv4_mini.sys Ver 188.8.131.5200 NVIDIA 20GB Maxtor ATA 100 HD Frequency / Voltage Control in BIOS CPU Host control Disabled Host DRAM clock Auto DIMM Over Voltage Normal AGP Over Voltage Normal CPU Voltage Normal Voltages as per Easy Tune 4 Vcore = 1.490 3.3V = 3.320 5V = 4.970 12V = 11.960 DRAM = 2.500 CPU = 1.500 AGP = 1.500 I have asked Gigabyte but no answer. Is the motherboard at fault or should I increase the DRAM voltage?