I press f9 and choose usb, but it does not boot, windows opens directly.

[Akif90]

hello dear hp. In my hand, hpnin dc 7800 passed, although I select my usb only from the boot screen, it opens the windows directly. Is there a solution for it? I tampered with the bios but could not find it.

[stevecomputer]

Your usb must be bootable also, and it must match your boot method, mbr legacy, or uefi.  You may need to turn off secure boot also.  If you are reinstalling windows then you can use Rufus usb boot maker to make a bootable usb to match your needs.

[Akif90]

Hello again. I already boot my USB with rufus, but the format screen does not show up every time so I have a ready usb device but unfortunately I cannot install windows even though I press F9 and select the usb device. Installed old vista bussiness versiyonu is opening.

[stevecomputer]

If the laptop is vista then when you are making a boot disk the settings will be for mbr and there will be a section near the middle for advanced drive properties and you need to choose "add fixes for old bios" You could reinstall windows using a boot dvd. 

[Akif90]

No, i was able todo a desktop compaq at first started doing this afterwards please help.

[stevecomputer]

What version of windows are you installing and what are you installing it on?

[Akif90]

windows pro 7 windows 8.1 Windows 7 Ultimate I tried, none of them detected and started the iso even though I said start from usb

[stevecomputer]

What are you installing on.  Did you try a windows 7 32bit dvd? 

[Akif90]

unfortunately I don't have a dvdim to write, ubmi was seeing it at first. windows is loading files freezing then start not to see it at all

[stevecomputer]

What are you installing windows onto, a laptop, a pc?