mac pro 10.5.8 is continuously rebooting...
my mac pro 10.5.8 is continuously rebooting and doesn't show anything except grey restart apple logo and loading spinning, then chimes and restarts again. what should I do?
I have tried holding shift key while rebooting, also
ctrl+R (even though it's not lion)
ctrl+C
MacBook Pro, Mac OS X (10.5.8)