How to create a disk partition

Hi,

I am a new MBA user, i installed Parallels and Win 7. Afterwhich I realised that they are all in one HDD, i.e. there is no disk partition. I did not install boot camp.

I would like to create disk partition such that my Win 7 system/ files are in the second partition (thinking that if there is virus in the windows platform, at least it will not affect my mac files in the first partition).

Is it neceesary to do that? and how can I create the disk partition now that I have already installed parallels and Win 7.

Thank you and appreciate any useful response.

R,
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