Could you provide the model of the CPU you have now and the new board you have in mind to use it in ?
The machine is nominally 2004/5 vintage. I was looking at a cheap MB and reuse the CPU with some DDR2.
The old board uses DDR
Why don't you get a 43 series chipset, the lowest cost would be a G31, or G41 but if you have a graphics card and don't want to use intel's built in graphics core the P43 series motherboards are the lowest cost and will run your older processsor most likely. Be sure to check the MFGs web site and stick with Asus or Gigabyte. Don't buy an off brand motherboard, or use a non Intel Chipset as it is best to use a Intel Chipset with a Intel MB. I buy from a place called newegg.com and they have an excellent return policy. Also, boards have user comments, so you can see what people are saying about particular MB's.
G31 - Most inexpensive around 50-60 dollars.
G41 - Chipset Newer, but still onboard graphics and same range
P43 Chipset, excellent for Ocing, and someone whom has alot of items to attach. You need your own graphics card. But if you play games you have one, and if games are not important any of the above are fine. There are also Intel versions, and even more versions of the same chipsets from the same MFG's, I am just doing this as it seems nobody is concered about your question. I would think an Intel Rep could direct you to intel's site to buy a board from Intel directly. You did not list any specs. The most inexpensive boards can be had for as low as 40 dollars. But you have to wonder about what was left out in order for them to be priced so low. Most likely stability issuse. My brother had the same problem and he bought a P43 and love's it. Price is higher around the 80-90 range and can be higher, and if you want the main stream board for the newer processors the P45 is the one to get and will run around 100.
Intel - 5 dollars less - http://www.newegg.com/Product/Product.aspx?Item=N82E16813121391
Could not find a P43 from Asus, but I did find an old 945G Intel branded motherboard for 79, and may be like the one you had?
Good Luck and may the force be with you!
In order to receive a decent answer, we need to know what the CPU is. Otherwise you might buy an incorrect mother board.
Pentium IV running at 2.8 MHz so its an old processor for LGA775 indeed.