A few options if HP Game Center isn't listed in Control Panel - Programs - Uninstall a program.
1) Use the Start Button (Windows Orb) then click on All Programs, scroll down to see if the HP Game Center is listed and if there is an uninstall option.
2) Go to the program folder and see if there is an uninstall icon.
3) No program folder? Do a Control-Alt-Delete (all three keys at the same time), open the Task Manager to find hpgamecenter.exe (or something like that) then use Windows Search to find the folder it is in. Look for the Uninstall icon.
4) HP Game Center may be running as a Service, type in services.msc in the "Search programs and files" box, if HP Game Center is listed then stop the program and then right click and set it to not start.
5) First locate the folder where hpgamecenter.exe is located as in #3, then using the Task Manager stop the program.
Then go back to the the folder location and re-name the file to hpgamecenter.exe.old
Wayne