Hi
how did you install operating system on usb drive?
what operating system?
If Dell Inpiron is new enough to have uefi bios it may offer 2 choices at F12 boot menu
uefi 16GB usb or
16GB usb
most programs making usb bootable do not support uefi
programs I use
pe2usb
rufus
there are several others including the Microsoft Windows 7 program to put a ISO of Win 7 onto USB memory drive
many laptops & PC's have problems booting from USB 3.0 ports but work on USB 2.0 ports
Modern Dells boot off any Windows or Linux USB or CD or DVD but may lack correct SATA AHCI drivers and not see the internal hard drive. (Usually only a problem with XP)
regards
Mike Barnes