How to reboot back?

Hi, I’m a absolute beginner, and I downloaded UB today,

But there are many problems with my laptop, such as lid close but can’t sleep, or can’t wake up after sleep, and can’t shut down except long press power button. Therefore I try to reboot back to ubuntu or windows. However, I download the unetbootin, and extracted files on usb, and press esc, only show me a grey grub text. How can I do to install back to Ubuntu or even windows?

sorry if this question bring any discouragement, but I truely need help.


I believe there could be two reasons for this problem:

  1. Unetbootin could have failed building the bootable image. You can try with other tools like Rufus, did, gnome disk manager.

  2. Boot loader could be faster than your keypresses. Some times it can be frustrating and might need several attempts to spam the correct key to trigger bios setup or boot from specific device. You should check what that key is for your laptop, and try to either hold it, or spam it, as soon as you power on. If it fails, do a full power off and try again.

I hope it helps