boot problem, help needed urgently

hey all,
i've got a very big problem with my macbook pro. i have two HDDs and i used to use both of them with my mac. i've always exchanged them with power off. but today, i forgot that my mac was in standby and exchanged the HDDs while it wasnt shut off. then i opened it up with a new HDD inside and mac os hanged itself up. so i pressed the power button to shut it off. unfortunately, when i wanted to shut it on again, it didn't work. i've got a bootcamp partition on this HDD and windows still works. however, mac os doesn't...when i press option during the boot, there is no mac os partition there, like it was earlier. i also cant start up from an install dvd. is there any solution to this problem??? what could this exchange have done to my HDD? there is so much data there and i don't have a complete backup and i need this data really, really urgently. any suggestions??