Bad news, mate. Your CPU is a socket 478, not a 775. However, I did find this for you:
Intel D865GLCLK Intel 865G Socket 478 mATX Motherboard w/Video, Audio & GbLAN Intel 4000888 D865GLCLK
$58 + shipping
It will handle up to 4GB (4 x 1GB DDR) of RAM, but XP (32-bit) will only access up to 3.5GB of RAM. That number includes any memory on your graphics card.
The mobo I linked to has an AGP slot, just like your current board, so if you do have a graphics card it will swap out without a problem.
This one has a PCI-E slot, but can only handle up to 2GB (2 x 1GB DDR) of RAM:
Biostar 945GC-M4 Intel 945GC Socket 478 mATX Motherboard w/Video, Audio & LAN Biostar 945GC-M4
$54 + shipping