trouble installing windows 10 on an old PC
trouble installing windows 10 on an old PC
You can sometimes boot from another device without altering the boot order. Instead of using the F key, consider selecting a different boot source. Have you tried removing the hard drive to check if the USB works? If it starts, it may help identify the issue.
Prepare USB for legacy boot first. UEFI USB won't function on older motherboards. Also, installing Windows 10 on a Pentium IV will be extremely difficult. If you truly wish to try Windows 10 on that old machine, install it on another device (in legacy mode), turn off any features that could slow the system, and then boot from the drive on the Pentium IV. Unless you have a lot of time. Avoid using an HDD on that old PC; an SSD is the only option for Windows 10 to work. Of course, a regular HDD will eventually boot you, but you'll be much older by then.