quote:
Memory
1. Type: DDR 400 / 333 / 266 support
2. Max capacity: 2 GB
3. DIMM slots: 3
Which DIMM slot are you putting the 1GB stick in? Always start with the slot closest to the CPU and go from there.
Also, I would try the memory in another PC of similar specs. as yours. If it works fine in another PC then its your motherboard. If it doesn't work, well... then its the RAM.
Also, your current BIOS might not support 1GB sticks. Try installing a new BIOS (be careful, 'cause you can feck up your mobo if you don't do it right). If all else fails, give Gigabyte a call and see if they have any ideas or support.
If you do update your BIOS, see if it says anything about additional RAM sizes in the release notes. If there is no mention of it support 1GB sticks, you might want to return it for a 2 sticks of 512MB DDR400, and then replace those 2x256MB with a stick of 512...
*EDIT
The specs of your board says that it supports 2GB of RAM... Then that means that it DOES support 1GB sticks... which is odd... because you can't make 2GB with 3 sticks of less than 1GB... Might I suggest calling Gigabyte, see if it supports HD ram