This is a pretty obscure problem, but I'm going to put a post up about it on the off chance I can help someone else out. My regular reader (hi dad!) will probably find this of no interest and should give it a miss 🙂
The situation I found myself in was upgrading a Boot Camp install of Windows Vista for the new release of Parallels Desktop 4.0 - no big deal, you may think. Unfortunately, I had forgotten that that particular install of Windows Vista wasn't activated, which caused the automatic upgrade process to bork, dropping me back to manual mode.
To complete the upgrade I needed to run the Parallels Tools setup executable. However, since I hadn't activated, I could only log in as far as getting the "please activate Windows now" screen. As it happened, I knew that I could get rid of this screen by feeding it the details of a Windows Vista license I own, but in order to do that I needed an Internet connection (I don't think my PAYG phone had enough credit on it for an extended Microsoft call centre experience). However, to get an Internet connection I had to install the Parallels Ethernet Connection drivers, and hence the Tools. Catch 22!
The workaround is convoluted, to say the least. First, we need a command prompt in the restricted Vista activation session. You do this by clicking any of the links in the activation window: they should cause a browser to open. From here, you can ask the browser to "Open a file" and direct it to C:\Windows\System32\cmd.exe - this should initiate "download" of the executable. Click the option to run the file and voila!
Now you have a command prompt the fun really begins. You might think you could just type D:\setup.exe and the Tools would begin installing, but life just isn't that simple - in Their infinite wisdom, Microsoft have imposed quotas on the resource consumption of the session they set up for the purposes of activation. This is probably the Right Thing to do from their POV, but it's just a pain in the arse for us.
The workaround is to get the internet connection working, so you can do the activation and hence lift the resource limits. To do this, create a floppy disk image containing the Windows 2000 drivers for a Realtek 8029AS adapter (you should be able to get those from here, until Realtek break their incoming links again). Personally I did this by using another virtual machine to download the files and extract them onto a new floppy disk image (you can create a blank image on the Floppy Drive tab of the VM settings). I would make the fruits of this labour available to you as a simple download if it were not for (unfounded?) fear of Realtek's highly trained attack lawyers.
Once you have the requisite image in your sweaty virtual paws you can proceed to mount it into the Vista VM. To finish up, type compmgmt.msc into that command prompt and update the drivers for the detected network adapter by searching for new ones on the A:\ drive.
You should now be free to run the online activation and break the Catch 22, allowing installation of the Tools - at this point feel free to help yourself to a cup of coffee and a ginger-snap biscuit to celebrate a difficult job done well (I know I did...).
I'm really quite suprised that I had to jump through this many hoops - the Realtek drivers allegedly come with Vista, for one thing. But - c'est la vie! It's also quite pleasing that the humble, long outmoded, floppy drive still has a place in solving modern IT problems 🙂