I installed many times Ubuntu in my ProBook 4530s along with Windows 8.1 but I can't boot that when I start the system, and also I fully installed the Ubuntu on my pc. But when the installation got complete it show me the message that "restart your computer" after restarting I can't boot that fresh installed Ubuntu.
So how can I manage my boot manager. I faced this problem so much and I installed the Windows more than 8 times in last two days
I have an HP 250 G1 with Win 8.1 and now Ubuntu, and I've gone through the same weirdness.
With HP firmware, you can probably tap F9 on startup, just as the HP logo is displayed, and be presented with boot device options.
Top of the list will be OS Boot Manager; that's the Windows Boot Manager. Then you ought to see one or two Ubuntu options listed.
There are two ways that Grub gets installed on a UEFI system (there is a third way, possibly, involving a Legacy Boot option in the BIOS and installing Grub in the MBR like we always used to, but I'll leave that for now).
One of the two Ubuntu options uses the grub.efi file (or grubx64.efi on a 64-bit system). This will only work if you have Secure Boot disabled, because this bootloader isn't signed.
The other Ubuntu entry will use shim.efi (or shimx64.efi), which is a kludge to allow Grub to start even when Secure Boot is enabled.
One or both of those will get you to a traditional white-on-purple Grub menu, from which you can boot Ubuntu.
There are bugs (or maybe just intentionally odd behavior) in HP's UEFI implementation, that make it difficult to run any other Boot Manager than Microsoft's. Lenovo firmware has quirks too - it's not just an HP thing.
There are ways of making the HP BIOS go directly to Grub. There are even ways of persuading the Windows Boot Manager to offer an Ubuntu option, but these are quite complicated and since I haven't fully explored them myself, I'm not going to advise on them here.
I can offer a link to a description of the EFI boot process, which might help to explain what's going on.
