If you Windows installed thru Bootcamp already you can access it from Mac OS X without having to restart in Windows. All you need is Parallels Desktop. Here are the steps to create a Parallels VM from Bootcamp partition:
Start Parallels Desktop and from File Menu click on New and select Install Windows from DVD or image File:
It’s extremely important to customize the settings, that where we are going to choose Bootcamp partition to boot from
In Hardware select Bootcamp partition instead of Image or DVD and that’s it
After a while you will hear Windows booting and you are all set.