You have an IDE hard drive.
You have DDR1 400 memory.
You have an AGP slot.
You have an 3GHz CPU.
You wil very rarely if at all find a motherboard without at least one IDE channel. No problem there. I am guessing you have and INTEL processor. You need to find a motherboard with DDR1 slots or one with DDR1 & DDR2 slots, if you pick a board without DDR1, you'll have to buy new memory aswell. I'm also guessing you have and SOCKET 478 board atm. I'm not entirely sure, but I don't think there is SOCKET 478 boards with PC-x slots. The new boards are LGA-775. The CPU's are different, they don't have pins, etc. So, you will probably have to buy a new motherboard aswell. The only SOCKET 478 motherboard I could find:
http://www.asus.com/products.aspx?l1=3&l2=12&l3=27&model=167&modelmenu=1Another thing to take note of. If you buy a new board, check how many IDE channels it has. If it's got only one and you have an IDE hard drive and an optical drive, you'll have difficaulties connecting all of that, aspecially if you have more than two IDE drives. If you had an serial ATA drive, it wouldn't be a problem. There are other solutions for the IDE problem, like an IDE PCI card, or an IDE to serial converter.
My advice to you is to save up some money, sell your old stuff and buy a new motherboard, graphics card, cpu and memory.
Some sites to check out:
http://www.gigabyte.com.tw http://www.intel.com
http://www.asus.com.tw
http://www.chaintech.com.tw
http://www.dfi.com.tw
I would recommend Gigabyte.
I don't know where you are from, so I can't really recommend a shop.