PS3: infinite green light and HDD fix problem!?

Ive had my ps3 a little over a year (and that means warrenty turned off) and my sister and her friend always shut it down from the back. I told them to stop, but one day they did it and when i re booted it it said the HDD was repairing and it restarted. It told me it was not shut down correctly and to restart it the right way. Everything on the XMB was loading, and i shut it off. Then came three beeps and the green power on was blinking. I HAD to shut it off from the back then. And now im in a paradox where all of this keeps happening. I dont want it to have the YLOD! What happened and how can I fix it? (overall, it still works. But the power problem is concerning me alot)