Sorry for not responding earlier, but the problem is that your question is a bit vague, and addressing it properly takes some effort. The big questions are what you want to share, what your current setup is, and what your restrictions are. I'll assume you have one OS X partition and one Boot Camp partition. You say you already have a normal VM created. That VM can share data with OS X by using Shared folders or network shares. If your Boot Camp partition is FAT, your shared folder could be located on the Boot Camp partition (OS X can't write NTFS by default).
Once you boot natively to Windows, you can't access anything on the OS X partition (Windows can't even read HFS+ by default). However, if your shared folder was on the Boot Camp partition, you're good to go.
The problematic setup is if your Boot Camp partition is NTFS. The simplest solution in this case would be to use a USB drive to share data. You could also attach the raw disk to the VM, since Windows knows how to write NTFS.
Another possibility is that your wording was poor and you're actually asking how to turn a normal virtual machine into a Boot Camp partition, which has not been done successfully to my knowledge.
