boot to safe mode
hello. i am trying to perform a long-overdue system clean-maintenance on my macbook running osx 7.5 and i can't boot to safe mode using the shift key. i am sure that i have tried every possible permutation of holding down the key during startup. i seem to remember an apple genius using a key combo -- control-7? - to startup in safemode when i had a problem way back... thoughts please. thanks so much!
MacBook, Mac OS X (10.7.5)