Cannot boot from usb

I’ve got the next problem: I decided to install lubuntu instead of Windows on my old pc(2gb DDR2, gt220, Intel Core 2 Duo stuff). Motherboard is ga-g31m-es2l, Award BIOS.
By some reason, I couldn’t boot from usb(I’ve set boot priority to usb, 1st boot device was hard disk, everything was fine and been done as lotta websites suggest to do).
Then I decided to install lubuntu via Unetbootin, but, by my mistake, I’ve formatted whole disks and therefore Unetbootin was also deleted, so now I can’t boot even Windows on pc(yeah, so stupid move by me). Anyways, the problem still occurs and I still can’t boot from usb(but I can boot from this usb from my laptop). Even now, when I’ve set usb with Windows instead of lubuntu, it doesn’t work anyways. Any suggestions? Should I try to update BIOS via Q-Flash, if I can to do so using Bios?
Another option is to unplug hdd and connect it to my laptop in order to install OS via it. But I wish there’s another option.
Thank you for future response!