macbook pro 17" 2007 replaced cpu fan will not boot

macbook pro mid 2007 running os 10.6.8 (snow leopard), newer 6 gb crucial memory, newer wd 500 gb hdd.

all has been great with this unit after warranty replacement of circuit board due to graphics issue.

i replaced the original hard drive with a wd 500 gb drive (got a full read) a few years ago which has been perfect.

removed and replaced right cpu fan and will not boot.

rechecked connections and all are secure.

hard drive will start-up then, within 4-5 seconds shuts down.

no start-up chime, display or lights during those few seconds.

have tried parameter ram reset.

performed system management controller reset (believe i got proper info to do smc reset for this model).

both to no avail.

the odds of a hdd failure just as i checked the fan would be like winning the lottery.

any ideas?