How to open encrypted partition, knowing the passphrase? (absolute beginner)

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http://askubuntu.com – I just installed Ubuntu 12.04 with the encrypting option. Soon after I found that I have lost my windows Vista and all my previous partitions as the in the new Ubuntu only one hard drive with summation of all previous partitions appears. As I needed my data I tried to recover the partitions. I was successful except for the Windows drive (dev/sda1) and that is because it is encrypted. Now, I even cannot run windows with Windows Vista recovery CD. Any help please..... Thanks (HowTos)