Right click a blank / empty area of the taskbar and choose Task Manager.
Select the Startup tab from along the top
Look for anything there that might be starting that reference HP
Additionally you might check here
Check C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp
And
C:\Users\YourUserName\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
AND you may want to have a look at your Scheduled Tasks, sometimes there may be a task scheduled to launch at startup or login (anyuser) to look for HP updates and such.