The only risk with a BIOS update is if you lose power. If you can protect against that then look over the how-to on the download page and also in the download itself there may be a read-me file. You can also contact your PC or motherboard maker's Support to help you with this.
I did not suggest to Reset the PC but to do a Repair Install which keeps your files, apps, and settings all in place which reinstalling Windows in about an hour, fixes most problems. It's a better install than the Reset if WIndows will start.
If you do a Reset be sure to back up your files and choose deep clean Reset saving nothing so it has you set up your account again, since a corrupted account can be the cause of many problems. Did you already do that step in the checklist I gave you? If so and you do a Reset then make sure to choose Cloud Reset so it downloads fresh installation files or it may use corrupted onboard files.
A vastly better install is the Clean Install which is the gold standard, better than any amount of money could buy. Look over this tutorial for an install that has been done by millions without anyone ever coming back with further problems that I have seen: http://answers.microsoft.com/en-us/windows/wiki...
Feel free to ask back any questions. Based on detailed results you post back I will have other suggestions if necessary.
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