Something not really related to Rainmeter directly.
I have found a way to remove the taskbar in Windows 7 only using a program called "Ultimate Windows Customizer".
I don't know if any of you have heard of it but it has functionality to remove the taskbar (and the start menu button) which a lot of people seem to want - why would you want to remove it??!!
Anyway, the download link is at http://www.thewindowsclub.com/ultimate-windows-customizer
How to do this?:
Click on the "Taskbar" button and select the options that you want in the "Misc Options" section
After enabling "Hide Taskbar and Start Button":
(No, I didn't 'autohide' my taskbar - it's actually gone)
Notice that gap at the bottom of my browser where my taskbar used to be. Highly recommended to set your rainmeter taskbar's position in that spot.
NOTE: IT WILL CREATE A RESTORE POINT JUST BEFORE IT APPLIES THE CHANGES
Just make sure you have your windows key working or a Rainmeter taskbar, so you can at least access the start menu!
Hope this helps!