7 Beeps on startup on a Dell system means a processor failure. I’d suggest that you follow the steps mentioned below and check for issue resolution.
Please let me know the findings.
I'm not the original poster, but the same thing happened with my laptop. I tried what you suggested but there was no change.
I looked up the cost for a replacement motherboard and they're like $150-300. I tried that with my last laptop when it died but the replacement only lasted another month or two. So, I'm not sure if I'll try that route again. Maybe though. In the meantime I got a new desktop - hopefully it will last longer.
For the record, this was an Inspiron 15r 5537, bought a year and 2 weeks ago.