iMac wont boot, makes loud noises...

Can anybody please help me, ok I usually have my mac set up for the display 2 shut off after 1 min. The day b4 I went back use it and it didn't respond, the light from the mouse was still on but it did not do anything. so I turned it off then turned it back on and it worked fine. Today it did the same thing and when i tried 2 turn it back on all i get is a white screen and a loud buzzing sound every 3 sec. please help!

If you have it, put the Apple original Disk 1 that came with your computer, reboot the computer, and hold down the D key (diagnostics). Run the extended test. Maybe the noise will be more obvious with that test, or you will get a failure code of some kind. Post any error code that you get, and someone may be able to help you decide what to do next.

Then maybe you can try rebooting from that same Disk 1, this time holding down the C key. Use Disk Utility from the Utilities menu, and run Repair Disk (different from Repair Disk Permissions). If that repairs errors, run the Repair Disk again, until no problems are found.

If that won't work, I suggest it's off to the Apple repair store. I think it's a power supply unit issue, but I can't be sure of that.

Thanks, 4 the reply I tried it but it didn't work, i guess i'll call apple care 2morrow, really kind of dissapointed in my mac. but yeah thanks again.