Storing credit card details

I have a business requirement that forces me to store a customer's full credit card details (number, name, expiry date, CVV2) for a short period of time.

Rationale: If a customer calls to order a product and their credit card is declined on the spot you are likely to lose the sale. If you take their details, thank them for the transaction and then find that the card is declined, you can phone them back and they are more likely to find another way of paying for the product. If the credit card is accepted you clear the details from the order.

I cannot change this. The existing system stores the credit card details in clear text, and in the new system I am building to replace this I am clearly not going to replicate this!

My question, then, is how I can securely store a credit card for a short period of time. I obviously want some kind of encryption, but what's the best way to do this?

Environment: C#, WinForms, SQL-Server.

Basically avoid by all means taking the responsiblity to save the CC details on your side, however I can assume you are using a thirdparty service to do your transaction such as PayPal/Verisign or whatever, most of them have API's that enables you to save CC credentials at their side, and they give you back a key that you can then use later to complete or initiate transactions, so they take care of the hard part, while all what you have to do is store this string key in your DB.

I don't believe it's actually illegal to store CVV info (in the sense that it's against any law), but it does violate Payment Card Industry rules, and they could impose any number of different sanctions. So, your requirements could actually result in you not being able to accept credit cards ;-(