Hello Fred. Sorry to hear about the problems you're experiencing. Couple of things you can try:
If you have a restore point that goes back far enough (before the first boot problem) you could try using system restore to roll back the computer to a good working state.
System Restore
Your computer might have some damaged or corrupt system files. Run a system file checker scan from an elevated command prompt (option two.) If problems are found, run the scan 3 times and restart the computer after each scan.
SFC /SCANNOW Command - System File Checker
You could also look through this tutorial to make sure you're not missing anything when attempting a startup repair. In particular, it's recommended that the startup repair be run 3 times and the computer be restarted after each scan.
Startup Repair
If still no joy, one of the Forum experts prepared a couple of troubleshooting tutorials with some additional suggestions.
Troubleshooting Windows 7 Failure to Boot Troubleshooting Steps for Windows 7
You might also consider jumping right to a repair install. It will attempt to fix your currently installed Windows 7 and try to preserve your user accounts, data, programs, system
drivers, etc. It takes about an hour to run. If successful you'd have to reinstall Windows Updates which could take another hour or two.
Repair Install
Another option might be to see if your computer has a hidden recovery partition put there by Dell. You may be able to access "PC Restore" in Step 3 and return your computer to factory specifications. Everything wouild have to be set up again just like the day you bought it.
How To Restore or Reinstall Microsoft Windows on a Dell Computer | Dell
And a final option would be to use this opportunity to do a clean install and get rid of all factory bloatware that slows down a computer.
Clean Reinstall - Factory OEM Windows 7