Re: [Trisquel-users] Thinkpad T420s 5 beeps

[aether]

5 short beeps means motherboard issue. But it is strange since you're saying  
sometimes it is booting.
Try what nadebula.1984 said. Clean RAM first. Then try with one stick only.  
(then switch with the other stick) See if it improves anything.
You might want to try to disconnect the CMOS battery for a few seconds.  
(clear CMOS)
Also try to boot without battery inserted.