hdd not detected?!?

ok....earlier I posted in a massive tizzy as I thought my hdd may have been wiped, however it seems this is now not the case. My Dell (vista) Inspiron 6400 is no longer detecting my hdd - but upon spending the last 7 hours looking around - I see that I'm not the first to have this problem - yet I cannot seem to find the answer. As the answers people seeem to be giving pertain to xp and other OS's...
I turned on my hdd this evening and all seemed fine, until I clicked on a folder in it - not realising that the hdd hadn't fully loaded yet. This caused it to crash - and since I have not been able to get wondows to see the hdd.
It has not assigned it a drive letter, yet it recognises when the hdd is connected, I have reinstalled the drivers and it tells me in the safely remove hardware section that everything is working fine - yet I cannot find my hdd anywhere?!?!?!

I have over four years of work on there - yes I know I know keeping it all in one place is incredibly stupid, and the fact that I was talking about backing everything up YESTERDAY makes me feel even iller.

PLEASE PLEASE PLEASE can someone point me in the right direction???
I feel slightly safer knowing that other people have encountered this - and that there is a (slim but still there) chance my data may yet be recovered.
If you can help me I'll love you forever, give you my firstborn, make you THE most delicious cake...and tell everyone I meet that you are withnout doubt the coolest person in Ireland.

please???
anyone??
wweeeeeeeeeeeeeeeeepppp!!!

x