Secondly, you may have come across some kind of bug which is fixed in a revision of the operating system. Lastly, you may have some new software which requires a newer version of the operating system. The most recent releases of the kernel sources are available on ftp.kernel.org . This site is mirrored worldwide so there is probably a fast copy of it somewhere near you. Then issue the tar zxf command to unpack it.
Patch files are much smaller to download than the whole thing.
If you do not need the very latest version, then installing a kernel source package from your distribution CD may be an easier way to proceed. The window menu lets you alter many aspects of kernel configuration. These dependencies may have been affected by the options you have choosen in the configure step. The make clean purges any now-unwanted files left from previous builds of the kernel. The last step is installing the new kernel.