You give no context, so nobody knows who specifically you're taking to task with this statement.
Go open up your PC and tell me there's no dust.
My direct personal experience differs with you, by a few dozen power supplies. Maybe 2 a year over the last decade, with an average of 100 machines being supported. Some years worse than others.
I think it would be wise for the OP to contact the computer professional mentioned to him by another local of his, and let the specialist handle it. Unless rebuilding it isn't a problem and there's no important anything on there, there may be just one shot here, and squandering it to count BIOS beeps or whatever you're proposing probably isn't the best way to spend that chance.
Dave Hinz