Press F10 after powering up the machine, which should bring up an 'Edit Boot Options' screen.
If it shows either of the following:
[ /NOEXECUTE=OPTIN /MININT
[ /NOEXECUTE=OPTIN IN/MINT
hit backspace to remove them, leaving only the /noexecute=optin, then press Enter to continue and see if it starts normally.
If it shows either of the following:
[ /NOEXECUTE=OPTIN /MININT
[ /NOEXECUTE=OPTIN IN/MINT
hit backspace to remove them, leaving only the /noexecute=optin, then press Enter to continue and see if it starts normally.