Did you compile IDE support in your kernel? What about PCI? Did you try building the kernel based on the .config from the old one if they are both 2.4 kernels? This stuff may seem obvious, but my first kernel build was a disaster because I misread something and turned off PCI support when I have a PCI/EISA hybrid system. The result was basically a non-functioning serial port and lots of error messages. BTW, kernel 2.4.17 has EXT3 as an option.
