Depends. What distro did you use and did it offer a option for kernel installation? If so, only install the kernel OR you could copy the kernel that boots your installation disc right to your startup disk.

Boot the DVD to the installer, then run terminal.app. It's under Utilities in the installer menubar.

cp /mach_kernel /Volumes/<startup disk name>

Example: cp /mach_kernel /Volumes/iMac

If your startup disk has a space in it's name, it's as follows:

cp /mach_kernel /Volumes/Macintosh\ HD

Also, I would suggest that when you first start terminal, you do the following:

ls /

This will show you a list of all the files in the root of the DVD filesystem. This way you know exactly the name of your kernel (some install DVD's have things like mach_kernel.voodoo as the kernel name). If the name is not mach_kernel, then just use the right name and it will most likely work and allow you to boot your system again.

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Mac OS X Leopard 10.5.8 (9L30) | Chameleon 2.0 RC3 | Intel Pentium 4 3Ghz 800Mhz FSB HyperThread 1MB L2 cache SSE3 1MB L2 cache works, cosmetic display of 512KB L2 cache | Asus P4V8X-MX VIA Chipset, VIA-VT8237 Southbridge | AC97 VIA8237 | Dual 1GB 333Mhz DDR SDRAM | nVidia PNY GeForce 7600GS 512MB 8x AGP DVI/TV-Out/VGA [NVinject 0.2.1; QE/CI/QuartzGL/Rotation] | Darwin Kernel Version 9.7.0: Sun Jun 14 20:48:28 IST 2009; Voodoo 2.0 Intel alpha3 :xnu-1228.12.14/BUILD/obj/RELEASE_I386 i386