How do I upgrade an existing Win7 installation to Bootcamp 4.0?

I am running a Macbook Pro i7 15", Mid 2010 model with three partitions:

1. OSX 10.7 Lion

2. HFS+ Partition where I keep my documents/downloads/etc...

3. Win7 64bit NTFS Partition w/ Bootcamp 3.3

All these partitions work fine. Unfortunately, I cannot download the Windows support software through the Bootcamp assistant because I get this error:

"The startup disk cannot be partitioned or restored to a single partition."

This message shows that the assistant is assuming that I want to setup/create a bootcamp partition, rather than just update my current Bootcamp installation. Am I going to have to trick the assistant into thinking I only have one partition? Am I going to have to backup the 2nd and 3rd partition and revert the drive back to a single partition in order to get the assistant to work.

It looks like the limited functionality of this assistant is going to force me to do a lot of extra work unless there is some way to to get the 4.0 drivers from somewhere else. If there is no workaround, could someone send me a DMG of their drivers?