Store and retrieve keys in microsoft key store

Hi,

I 'm looking for storing (and thus retrieving) a key in the microsoft key store. We are using windows server 2008. I would like to know:
- in what format is the key stored?
- what .NET call to make to retrieve the key?
- what .NET call to make to store the key

Taking a step back I'm also looking for ideas on how to best secure the key:
- against admin retrieval (can we limit access to a particular AD group?)
- against server failure (how to retrieve the keys during server recovery)

Taking one more step back, when is it best to use database encryption (using SQL 2008) vs data payload encryption. The objective of encryption in this case is to ensure different users have access to only their data in the database (thus encrypting the data which is not theirs).

Thanks very much for your help!
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