Invoking Mac processes from Windows

I'm about to install Windows 7 via Bootcamp, but have a few questions first:

1. I plan on running a database program that makes changes to metadata in photo files (IDImager). This database will be run in Windows. I want to read and write files on my OSX partition or an external hard drive. Can I do that? Or am I limited to only the Windows partition?

2. This same database program allows you to set up opening an external photo editing program by double clicking the thumbnail, or by right-clicking and selecting "open with". If I were to use Parallels for VM, would I be able to select an OSX application to "open with".

3. Does Windows 7 via Bootcamp allow accessing external drives? (Sounds like it does, but just want confirmation).

thanks for your help.

Both Parallels and Fusion allow for sharing files and folders. So yes, it's possible to open a file on the Mac side from a Windows VM. I do it all the time when I run my XP VM from Fusion.

Windows 7 run from a Boot Camp partition is the same as running native Windows 7 on a Dell or HP. So yes, it "sees" external drives.