Heres some brief steps to get you started. You should have a strong understanding of windows security (I'm serious about this, you don't want to lock out your account), and of course good SVG knowledge.
*this is all from memory, so correct me if I'm wrong. XP professional was used*
-Browse to your c:\documents and settings\%USERNAME%\local settings\ folder.
-Right click the 'temp' folder.
-Go to the security tab
-Set the advanced permissions for the local system account
-Click the 'deny' checkbox for 'delete' and 'delete folders and files'.
-Set the permissions so they apply to all child folders and files.
-Launch theme builder
-Export the default theme to the desktop (don't make any changes for starters)
-You may get some windows security errors
-Go back to that %USERNAME%\temp folder and find the folder with the latest modify date
If you did the above correct, the folder should contain the ribbon's default SVG files. In these files, you will find the objects to tons of stuff, that if done properly, you can control with SVG.
Play around with it. Build up an new SVG, and import it to your homescreen/lockscreen of theme builder.
Don't forget to set your security settings back.
I'm sorry these instructions are so brief, and pretty dangerous. I advise you to not modify windows security unless you really know what you are doing.
Like I said, I'm working on putting together some demos and shares to make this a whole lot easier for everyone.