Hello.

I have Inspiron 5558 and after changing hdd to SSD and adding more ram it was running very fast, Windows started in 5 seconds, everything program was loading in less then a second. 

Yesterday I've downloaded and started SupportAssist to check for driver updates but it did not start or maybe it started but did not show any window... so after waiting half an hour and decided to manually check which drivers I need. There was only critical BIOS update. I've updated BIOS to A17, restarted and after that everything started working so slowly that even to start Google Chrome it took 5-10 minutes...

I've downgraded BIOS to A16 but nothing changed, it was still extremely slow.

Then I downgraded BIOS to A15 - the same...

Now I upgraded again to the latest version of BIOS, ran quick tests - they passed. Then I ran full tests - they haven't finished...

Now my laptop it working slowly and I have no idea what to do...