Tried to boot up a computer, got error-invalid disc

not told what is on that USB drive.
not why needing any usb to boot.
I do but it has w10 installer there, and put there by MS.

When booting, try going to the Boot Menu by pressing F12 when you see the Toshiba logo so you can select your hard drive as your boot device. After doing so, if you still get an "Invalid System Disc" error, then your hard drive may be shot.

This issue is often caused by either an incorrect setting in CMOS Setup or a bad boot device, such as a bad hard drive.

1. Verify your boot options are properly set in CMOS setup. We recommend having the CD or disc drive as your first boot device and then hard drive as the second boot device.
2. If your CMOS Setup has an option to boot from the LAN disable this option.
3. If you have changed any CMOS settings, make sure to save and reboot the computer.

If this does not resolve the issue, try resetting the CMOS values to the default settings, save and exit.
Finally, if none of the above suggestions resolve this error go through the Invalid or Non System Disk error troubleshooting steps, which is related to this error message.

You have to go into your BIOS and select booting from Disk not hard drive when i say disk i mean either the cdrom or dvd disk players attached to your motherboard. also you can get a boot disk to try that at the link below.

http://www.allbootdisks.com/download/98.html

for this you need a system recovery discs or boot discs just insert them and follow the instructions

eighter from windows boot cd or dos disk run fdisk or run chkdsk and then try to format from the boot cd or boot floppy

can you get into the BIOS? if so, change your boot order to cd-rom first.

This might be simple.
Assuming your son didn't make any internal changes to your computer. The problem may be that he changed your boot sequence to boot to floppy or CD instead of the Hard Drive.
Do the following:

As your computer is starting you will briefly have the option to hit F8 (I think F8 Might be another) for "start up menu or options".
This will take you to a screen of text where following the on screen text areas and moving the curser with the keyboard arrows and enter or escape check your boot sequence (the order of where your computer is to look for start up information)

It should read as follows:
#1 HDD1 (this text may vary)
#2 CDROM drive
#3 FLOPPY (if you have one) or other removable drive

If your son changed this and forgot to it back your computer may be trying to get start up information from a CD or Floppy instead of your hard drive.

Once you've changed this (assuming you needed to change it) following the instructions use the key to "save changes and exit"
Your computer should now boot up correctly.

Let me know if this helps

Do you have Roxio or Easy CD creator installed on your PC?

Check the floppy drive to see if there is a disk in it....if so, remove it and try booting up the computer again.