I haven't tried Boot Camp in awhile, and when I did - I did not have Microvellum installed. But yes, rivendellwood is correct - Boot Camp just makes your Mac partitioned so you can boot into either Windows or OS X. In OS X, you could load up your Boot Camp partition inside of Parallels. I did this when I had Boot Camp installed a year back or so and it seemed to cause Windows (inside of Parallels) to go into 30-day activation mode because it saw the Parallels machine as a "new computer" and deactivated itself. But, when I booted back into Boot Camp, all was well.
I've noticed that Parallels boots windows a lot faster than natively (probably because the virtual machine requires minimal drivers compared to a "real" machine and I/O and IRQ/ACPI requests aren't as hard for it to acquire compared to a real machine) and some actions are faster, but in general - AutoCAD in "coherence" mode in Parallels is a little choppy when running a command (line, copy, any command). 3D mode (solids and orbit) in AutoCAD does however seem to be smooth - unless of course you're moving an object from base point to wherever - then it's choppy as said above.
In AutoCAD 2005, there was an issue while in "coherence" mode in parallels that if I opened properties on something it would cause Parallels to crash - but it worked fine in "window" mode. AutoCAD 2007's properties works fine in parallels in "coherence" mode but active commands cause the cursor/crosshair to become choppy.
No matter what, there's tradeoffs. Ultimately, I would not run AutoCAD in Parallels except for testing purposes (snapshot manager is useful) or in a crunch when no "workstation" computers are available. It would be better in "native" mode and in that case - you might as well get a HP or Dell with similar hardware specs (Core 2 Duo) and pay less money.
Although it is nice that when Windows blue screens or just crashes that OS X is still chugging along...