INSPIRON 2330 & WINDOWS 10: Slow Boot

I have an Inspiron 2330 that has been upgraded to Windows 10.

However, ever since I've upgraded, it takes a long time to boot up and there is a dark screen for up to 30 seconds before I get to the desktop.

I've reset the machine back to factory settingsand reinstalled Windows 10 -- and the problem has not gone away.

All drivers (including the BIOS) are up-to-date.

Any suggestions on what might be going on?

Thanks,

pj