The one beep, two beep is a BIOS error for the graphics card/screen.
You could try to boot a live-cd, perhaps the same openSUSE 11.2 you are using, or something like SystemRescueCD, to check that the is no hardware fault. If you can get a POST, try to look at the BIOS settings to see if you see anything that you can change for the graphic or screen.
If there is no hardware fault, the easiest thing may be to do a new clean install. If you succeed, you might use the command "lsmod" to see which module is loaded for the Radeon chip. If the system is stable, you can use that module; if not you can change to a more basic module or try to reconfigure with "sax2". If you were to use the DVD to install 11.2, you would have the ability to see and select the packages that will be installed.
The fact that the system will not POST is not a good sign, but installing linux should not have killed your hardware.
The next thing you might try is to clear the BIOS by setting the right jumper on your motherboard. You should see your system manual or google for the details.