New
#11
what exactly do you mean by refusing to boot from flash usb? if you just connect the flash usb and you press nothing when you are restarting then it will ignore the flash usb and start windows. you should press a button a few times (for me that button is esc) just after you restart and before anything shows on the screen. after that it should ask you if you want to start bios or go to boot manager. go to the boot manager and you should see the flash usb listed there. select it and it will boot from the flash usb
if you are happy with your current hard disk then buy new one which is exactly like it. if you want to buy a different type of hard disk then you need to open the desktop and look at the available hard disk slots in the motherboard and see how many slots you have and the type of each one and then pick a hard disk and buy it. if you are unsure then ask someone experienced to come and examine your motherboard and tell you your choices