Using a Boot Camp Partition for both VM and Dual Boot

I just installed Windows XP to a Boot Camp Partition on my MBP. However, rebooting is a hassle and naturally I want to avoid doing such as often as possible. I think running Parallels Desktop would suit my needs quite well. But here's the catch: I want to be able to use one partition to serve both of those needs. In other words I want have the option of booting through both Boot Camp or Parallels.

How would I go about doing this? I already have a XP installed via Boot Camp. So if there is a method where I don't have to reinstall, great, but I am fine with deleting stuff.

 

Thank you very much. I just downloaded the trial of vmware fusion and it works wonderfully. This is exactly what I needed.