Late 2009 iMac start-up problem

[Wing]

My late 2009 iMac encountered start-up problem in the last 2 weeks. It could not start-up sometimes, however, sometimes it could start-up normally.
In one successful start-up, after entering the desktop and using the computer smoothly for awhile, there was a loud noise of the fan.

Anyone could suggest what might be the problem? Ram or logic board?

Please help. Thanks!!

 

[justperry]

My late 2009 iMac encountered start-up problem in the last 2 weeks. It could not start-up sometimes, however, sometimes it could start-up normally.
In one successful start-up, after entering the desktop and using the computer smoothly for awhile, there was a loud noise of the fan.

Anyone could suggest what might be the problem? Ram or logic board?

Please help. Thanks!!

Run Apple Hardware to see if there are any Hardware issues.

Intel-based Macs: Using Apple Hardware Test