Help - Tried installing Ubuntu but ended up messing PC up.

Hello Robert22 Welcome to the Ten Forums!

And also a welcome to the "Trash MBR Seminar" you got introduced to apparently courtesy of Open Source! Been there done that once upon a time ago so don't feel all alone!

The first thing you will want to see tried out will be the Startup Repair option found in the Advanced repair options while booted live from the 10 media if you saw that made up. Many opt to see the Recovery Drive made up with an 8gb or large usb flash drive using the Backup & Recovery option for that found in the Control Panel to save on the need to pull out the media all the time.

Those two guides work hand in hand together at times if you opt for the Recovery Drive you can simply boot live from that. The HP recovery media for that model if seen made up with a recovery app(optional) might help you with the factory 7 OEM install but not with a 10 upgrade if you saw 7 upgraded. You would first need to get into the present Windows installation in order to start the revert backwards from 10 to 7 if that was the case.

What most likely did happen however was seeing the ubuntu 15:10? Installer put the GRUB boot loader on the drive which automatically overwrote the Windows mbr information. If you have the 10 media and the Startup Repair should fail the next step would be running the "Bootrec /rebuild" command at the dos like prompt to see if the boot repair option will rewrite the mbr for you. With the DiskPart tool you could also use the "list disk" and "select disk #0, 1, 2, or" commands and then type "active" after selecting the correct OS drive to see the primary made active as an alternate.

Night Hawk all they have to do is a Fix MBR. The problem is that if they do not install Linux properly, the Grub replaces the Boot.ini for Windows.

This is why it is always best to back up before doing anything. If I need to go back to Windows, I will just image my last copy of Windows. As for the OP,

This is the exact process that the OP needs to do, in order to Fix the MBR:

The command in Windows 8/8.1/10 for fixing MBR is "bootsect.exe".
bootsect /nt60 drive_letter: /mbr
this fixes boot record of partition mapped to "drive_letter:" and the MBR of the disk where the partition is placed.
C:\Windows\system32>bootsect

bootsect {/help|/nt60|/nt52} {SYS|ALL|<DriveLetter>:} [/force] [/mbr]

Boot sector restoration tool

Bootsect.exe updates the master boot code for hard disk partitions in order to
switch between BOOTMGR and NTLDR. You can use this tool to restore the boot
sector on your computer.

Run "bootsect /help" for detailed usage instructions.
Alternatively you can use "Dual-boot Repair Tool" which has a graphical interface to bcdboot.exe, bootsect.exe and other useful functions like boot sector view and ... one click dual-boot repair function for Windows 10/8/7/Vista (also can fix Windows XP boot files).

The fix mbr command isn't always that simple to use anymore. You are thinking XP, Vista, and 7 while since 8 things in the boot sector have seen some changes. Now the repair tools are needed a bit more.

One thing you should know if you decide to try using the Startup Repair you may need to be run a few times for that to work while booted live from the 10 media. Often the first run won't do anything where it then needs the repeats to see things corrected.

Well one thought is to keep the Linux install isolated from the planned 10 drive unless you can work with Grub 2 any. For seeing both on the same drive you are much better running ubuntu on VM Player or enabling the Hyper-V feature that actually offers a bit more as far as settings and network switches go. The two generally won't together however so if you enable the Hyper-V don't plan anything with VM ware. But the VM will keep you from trashing the boot sector again!