can I use bootcamp if already using parallels?

Hi - This is my first post so I hope I am in the right place! I had Parallels and WIndows 7 installed by the apple reseller who sold my my macbook pro so didnt set them up myself. I have only occasionally used windows in parallels so speed has not been a big issue. I am now using it more and it can run very slowly particularly during start up and shutdown rendering the machine pretty useless for 5-10 minutes or more. It doesnt crash it just takes an age to boot up windows via parallels or shut down windows in parallels.

I am assuming that the machine is struggling with processing power and/or memory to run both operating systems and the software packages in each. I am thinking a solution would be to boot up and run windows on its own in boot camp to give it all the machine's power and I can cope with not having both operating systems up and running together. I would just boot up in Windows for a while when I need it.

My question is can I use the Windows 7 operating system from wherever it currently resides on the hard disk to run it in boot camp or do I need to reload it using bootcamp (via the boot camp assistant)? OR - is there any other trick to make parallels run much quicker?

My sustem is :

MacBook Pro

13-inch, Mid 2010

Processor 2.4 GHz Intel Core 2 Duo

Memory 4 GB 1067 MHz DDR3

Software OS X 10.8.5 (12F37)

The Parallels I am using is:

Parallels Desktop 8 for Mac

Build 8.0.18608

(Revision 898384; July 17, 2013)

Many thanks