Without enter the bios, in some PC you can choose from what device boot, simply with F11 key.
You will prompt for the device you want start from (an usb one or a partition of your PC).
problems with an encrypted partition
In Linux you could face an impossibility to mount a crypted partition.
The command that could be useful then are
1. sudo dmsetup ls --tree
2. ls -l /dev/mapper/
3. sudo dmsetup remove /dev/dm-0
You have to replace dm-0 with your result in 2.problems with an external hard disk
You could have problems with an external hard disk, such as safely removing it (even after unmounting it). In this case you could try this code:
sudo hdparm -Y /dev/[your device: something like sde1 or sdh1]Another problem could be the impossibility to mount your external hd. In this case, if the hd has an ntfs filesystem, you could try this code:
sudo ntfsfix /dev/[your device]I found this last code on www.makeuseof.com.
problems with an external (usb) hard disk
If you get this error message: can't read superblock on /dev/sde1
you can try to fix it by the following code sudo fsck -yv /dev/sde1.