|"They're both Windows XP machines"|
XP is designed NOT to be transferred from one machine to another. Unless the hardware, especially the motherboard/chipset, is virtually identical, Windows will detect the difference, display a blue screen & that's as far as you'll get. Here are the specs to both systems:
Notice that the 2300 is based on the Intel 845GL chipset, supports only 400MHz FSB, uses outdated PC133 RAM (max of 1GB), has only PCI slots & most importantly, does NOT support SATA.
The 4700 is obviously much newer. It's based on the Intel 915G chipset, supports up to 800MHz FSB, uses DDR2 RAM (max of 4GB), has a PCI-e x16 slot for graphics, & does support SATA.
What you have in mind won't work, & even if it did, it would be a substantial downgrade. How about telling us what is wrong with the 4700 & how you came to the conclusion that the board is the problem?