I don't know which shortcut keys, if any, but usually what I do is 'Start' 'Run' type Msconfig. Tick 'Diagnostic Startup' which only loads basic devices and services at the next boot. Or you can select 'Selective Startup' open the 'Startup' tab and un-tic the offending program and reboot. Also, you can repeatedly poke F8 during POST and select Safe Mode. Then uninstall the offending program.