Macbook stuck at login screen My macbook is stuck on the login screen after entering the password. I've been using this MBP for the past 4 years and it's been slowing down of late. However, I'm now having trouble logging in to my primary account: after I enter the password, I can proceed no further, although I still have access to the Guest account. 

I've gone through some of the steps mentioned here and in other forums: resetting PRAM, reinstalling MacOS, etc. I ran disk utility and I'm getting an error. What should I do?
You need to backup the disk ASAP before your data is lost.  Then replace the bad hard drive and I would reinstall macOS from scratch on the new drive.  Last copy your data back to the drive.  If you have a time machine backup you can restore that to the new hard drive in one step.

Give us some model info on your Mac and we can advise you more.