Q: MacBook Pro 2010 beeps and shutdown.

Hey Jimmy, thankyou for your response. However, if you read carefully my post, those sounds never happens during startup, ONLY when computer is already in use.

As i wrote in my original post, I've already performed a SMC reboot, to no avail. I would have ran an AHT but I lost my original cds that came along the Mac, so that's not an option. However, I ran some test with TechTool Pro, and passed all tests.

Sorry mate, but can you read what I wrote? I didn't put any thermal paste yet, I've only bought it. I just wanted to know if those 3 beeps can be related to a overheat issue. I see that you want to help, but If you don't know the answer please stop replying.

Yeah, I've thought of the logic board too. Unfortunately, if that's the case, it would result in me not wanting to replace a 6-years old MB logic board. I'll try contacting someone at Apple as you suggested, thankyou.

That's what I wanted to know, thankyou. Because I couldn't find one single forum, post, article with an explanation of beeps during use and not during startup. That seems to be the issue, anyway: I've just swapped one of the banks (2x2gb) with another one from another Mac and everything seems to work fine until now. Tomorrow I'll go buy two new Crucial banks (2x4gb) and test it a bit.