MacBook a11811 early 2008 keeps restarting over and over
Early 2008 MacBook a1181 keeps restarting
Early 2008 MacBook a1181 keeps restarting
Please determine if the same problems occur in "Safe Mode": Use safe mode on your Mac - Apple Support.
If you are still unable to log in, you will need to boot from that Mac's original, grey, System Install DVD to "repair" its startup disk. It may or may not be successful.
MacBook a11811 early 2008 keeps restarting over and over