Black screen 60+ mins to boot

[rudge]

Toshiba satellite - running windows 10 - ran fine booted quickly for several months after install of windows 10. Last few weeks when powering on - black screen for 60+ minutes and then the logon screen appears asking for password and notebook runs fine. ran disk check - and no issues, anti virus up to date, -
since I can't stare at screen for 60+ minutes no idea what appears on screen prior to prompt for password - glance over at pc from time to time and eventually see logon screen. Tired safe boot and same thing. sometimes if PC doesn't boot within 60-90 minutes I have to hit power button to kill power and then attempt power on again - and wait.
OS Name Microsoft Windows 10 Home

Version 10.0.10586 Build 10586

Other OS Description Not Available

OS Manufacturer Microsoft Corporation

System Model Satellite L55-B

System Type x64-based PC

System SKU INVALID

Processor Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz, 2401 Mhz, 2 Core(s), 4 Logical Processor(s)

BIOS Version/Date INSYDE Corp. 1.50, 7/7/2014

SMBIOS Version 2.7

Embedded Controller Version 1.60

BIOS Mode UEFI

 

[Cycloid Torus]

Unusual problem... might be conflict of anti-virus / anti-malware. What else do you have which might conflict before logon? Malware?

 

[rudge]

Only anti virus I see running is webroot secure anywhere but have had that for a while

 

[Cycloid Torus]

If it isn't AV conflict, then likely to be malware. Can you boot from a Ubuntu Live CD in a couple of minutes? Then I would try BitDefender Rescue CD ( http://www.bitdefender.com/support/how-to-create-a-bitdefender-rescue-cd-627.html )