As one of the few, the proud, the VC6 users, I figured I'd post my experience installing it on Vista for posterity. Welcome to all of you viewing this from the future (or 2007, as I am calling it currently).
I started with:
Vista RTM Ultimate
Visual Studio 6 Enterprise
October 2001 MSDN
February 2003 Platform SDK (all CAB files unzipped and burned to CD)
Before we start: Vista will show some warnings about programs having compatibility problems with Vista. Since I use VC6 for work, I threw caution to the wind and ignored the warnings. I've had no troubles yet.
Run the VS6 installer. The first thing it will do is update the Java VM. Once that's done, let it reboot the machine.
Once you've rebooted and relogged, the install wizard will come up automatically. Close the wizard right away. The wizard is not running elevated, so it won't be able to do its job.
Rerun the wizard and install the VS components you want.
When you get to the part where it prompts you to install MSDN, I said no because I'll install it later. Continue on with the wizard (I don't install any of the additional stuff) and finish the process.
Put in your Oct 2001 MSDN disc and run the installer on the disc. I had no hiccups at all installing this.
Run VS6 once and close it right away. I got in the habit of doing this because years and years ago, the Platform SDK wouldn't install if you had not run VS once yet.
Install VS6 SP6. Again, I had no troubles here. Run VS once and close it just to be sure.
Install the Platform SDK. Because the installer uses an ActiveX control, you'll be stuck if IE is not your default browser. If this is the case, either make IE the default temporarily, or drag default.htm from the root of the disc into IE. IE will ask you if it's OK to run active content to run from the local machine, say yes.
Use the PlatSDK Visual Studio Registration tool to add the PSDK dirs to the VS include and lib paths.
Optional: Create a shortcut to msdev (I pin it to the Start menu) and set the shortcut properties to always run the app elevated. I need to do this because otherwise I can't build DLL COM servers; regsvr32 needs write access to HKCR and HKLM, which it won't have unless the IDE is running elevated.
Run VS6 and enjoy your IDE! In beta 2, MSDN didn't run unless it was elevated, but this has been fixed in RTM.
I also use the WMP 10 Player SDK and that too installed without a hitch.
Step 0: use Notepad to create a file named msjava.dll (use "" around the filename to stop Notepad adding a .txt extension) in Windows\System32.
This fools the VS6 installer into thinking that the MS Java VM is already installed, so it does not run the VM installer. This means that it won't prompt for the reboot so steps 1 and 2 are not required.
If you have already followed these steps go to Change/Remove Programs and uninstall the Microsoft VM. The version that VS6 installs is highly vulnerable to attack.