I have a Dell Inspiron N5050 laptop about four years old which has been working fine up until now.

Today, when I turned it on it goes to a blank grayish screen and just stays there.  I've tried rebooting several times and it always does the same thing.  Here is what I see:  The Dell logo then the blue Windows 10 logo and "Please Wait a Moment" at the bottom then the gray screen forever.  After about 5 minutes I sometimes hear the little Windows start tune which usually means it's all set to GO but I still just have the gray WINDOW. 

I finally got into Safe Mode and uninstalled Bitdefender because it has been CAUSING problems on both my laptop and desktop.  Since I installed Windows 10 on both, the Bitdefender problems have gotten even worse.  I have to uninstall it and reinstall it to fix whatever problem it is causing.  Still the same gray window after uninstalling it, though.

Here are the messages I was getting before I was able to get into Safe Mode:

RECOVERY

It looks like Windows didn't load correctly.

Choose advanced repair options for troubleshooting tools and advanced options. 

I clicked "See advanced repair options"

Then I clicked "Reset or Troubleshoot"

Then I had a choice of:

"Reset this PC" or "Advanced Options"

I clicked "Advanced Options" and was able to choose Safe Mode where I uninstalled Bitdefender.

If I go back into Safe Mode I don't know what to do at this point.  Should I reset?  Will I lose all my files if I do?  Advice welcome, please.
Do you have a backup plan?
You might need to install everything again and get your personal STUFF from tghe backup archive.

When a laptop gets old, there are three of four areas that need attention.
1. Dust build up may increase the heat load.
2. The CMOS battery may have failed.
3 The hard drive might be  unreliable. Or the RAM.
4. The battery has gone bad.

The Windows recovery works good if the errors are few. But it can not repair big damage to the OS or programs.
Thanks for your reply and the info.

If by backup plan, you mean, do I have Windows 7 on a disc, I don't.  I could never get it to work.

It is giving me the option to reset.  Should I try that first?

Or is there something in Safe Mode that might help?

1) Can I open it up and clean out the dust?
2) I don't know what a CMOS battery is.  Can it be replaced?
3) Is there a way to tell if the hard drive or the RAM are the problem?  I have gotten a couple of messages lately saying the memory was low.
4) The battery worked yesterday but I have it plugged in now.

Is Windows recovery the same as "reset"?

I'm moving in 4 days and I was just about to pack my desktop and rely on the laptop but then this happened.  I don't have a smart phone or a tablet or anything else I can use.
I figured out how to run a full diagnostic on my laptop (which took almost 3 hours) and everything showed up as OK.

So I decided to go with the reset that would leave all my files intact and it worked.  Whatever was keeping me from booting is gone now.