Alright, so I tried to install the windows 7.8 update via Zune and it kept saying my phone was up to date, I tried the disconnect trick also and that didn't work. Me being me, the impatient one, I tried to use third-party software to do it, it was working and then it seemed like it froze, I waited five minutes and nothing changed. So I unplugged the phone to turn it on and now it's bricked, I think. I'm un sure as to address it in the correct term. But it keeps coming up with the picture on it saying not to disconnect it from the PC. OR, when I hold down the power button and release it, it vibrates. Every 5 minutes it vibrates by itself.
Also, I've tried a hard AND soft reset and nothing's worked. I don't know what to do.
If you have tried a factory reset, then take it into place of purchase with receipt so it can be sent to the repair center for software re flash/recover. There maybe a software reload charge if it's deemed a cause by your actions.
If it's displaying do not disconnect from PC, does Zune see the phone? If so does a restore work from there?
I've had similar issues a couple of times when it seems to have died(nothing to do with updates). Solution was put it on wall charger(USB was causing the issue) for a while (hour or so) and it started up by itself. Sounds like a different problem but might be worth a try.
You can do factory reset you can do by holding volume down, power and camera buttons until it vibrates.