Dell will boot and freeze before reaching log in screen. Will only function in "Safe Mode". I have run all diagnostics and no problems detected. What could the problem be

There's some program or driver that is loading up when windows starts "normally" that's no when it starts in safe mode. Have you recently installed any new hardware? Webcam? Printer? Harddrive? if you have, go to device manager while in safe mode and remove the driver. If you installed a new program that runs automatically during start up, then use MSCONFIG to change it from starting. Again, do this from safe mode. Go to start > run >TYPE: msconfig and then ok, and then the tab should be called "startup". one of these two things are most likely the problem because like you said it boots in safe mode no problem, Safe mode had the computer boot with only the bare minimum drivers/software needed for start up. If neither of these two things work, then, (again, in safe mode) right click your hard drive from My computer > properties >Tools > Check now (under error checking)

Hope this helps you solve it

It's stuck on the blue screen. This happened after starting a restore point and I dropped the battery out before it was finished.

It could also be a very bad virus. If it was a driver then you most likely get a blue screen- but not always. I suggest you download spyhunter and run a scan with that in Safe mode(with networking) per Ausified instructions and see what comes up- if theres a virus hindering your start up spyhunter will catch it.