There may well be a hardware issue as it seems Windows is discovering your touchpad during a boot. This shouldn't happen under normal circumstances. If you know how to get into the BIOS then you may find a hardware test option - if you feel confident about doing that then that's the first thing I would do - just to ensure that the hardware is okay. However, if you're not confident of booting your machine and accessing the BIOS then I wouldn't do it. Be sure not to change any settings in the BIOS if you do boot into the BIOS.

Within Windows I would run a full virus-scan and also a malware-scan (I don't what anti-virus tools you have on your machine). There's also a possibility that you've got a browser-hijack.

If you're using WiFi, are you sure you are connected to the same WiFi connection that you normally use? The 'unknown computer' or 'unknown device' message is interesting. Can you clarify what the exact warning from Yahoo is?

Have you been sent an email recently saying you're connecting from an unknown device and giving you a link to click on? Perhaps that was a phishing email?

I would also try a different browser to eliminate Chrome as the root cause (the problem could be cookie-related). I would recommend Firefox.

Finally, I wasn't trying to get you to run any cleaning software from my first post! I was merely asking if you have run anything like that previously. On occasions some cleaning software can be a little aggressive and remove things that should not be removed. However, the default settings of CCleaner are usually fine. You almost always get loads of Registry keys that are not needed anymore.