What should I do? My password isn't working?

I have 2 yahoo accounts. This is the first one and I use it mainly for yahoo answers. The second one is more important but I can't sign in now, but I'm pretty sure my password is correct. I think someone may have hacked into it. I tried resetting my password but I can only remember the answer to one of the security questions, and the email I had put as alternate is an msn account and it's an old one that I don't use anymore, in fact I think someone hacked into it as well cause a couple years ago I tried to sign in but my password didn't work, even though I was pretty sure it was the correct one. After that I just abandoned it because I didn't really need it. I contacted the msn customer service to try and recover the msn account so I can use it to recover the yahoo one, but they're not responding. What should I do? That's 2 of my email accounts already, and I think they have been hacked into by the same person. I don't really care about the old one (the msn one), but I really need this yahoo account. Please help.

Also, is it possible that an account gets deactivated or deleted or something after I stop using it for a while, and if so how long does it take for that to happen?