Easiest is to drag the named User folders which are being used to external to transfer to new install.

You do not want AppData as it is a corruption path. Start fresh with new settings.

If you want to try to troubleshoot the old install here are steps for Troubleshooting Windows 7 Failure to Start.

I would first test the hardware by booting into Dell Diagnostics: Dell Diagnostics Utility - How to Run the

Follow these steps to get a perfect Clean Reinstall - Factory OEM Windows 7.