Your Mac is not an iMac G5, but rather an Intel Core Duo, specifically it is the:
17-inch iMac (Early 2006)
according to:
http://docs.info.apple.com/article.html?artnum=301724
It can not have its stand removed. It is not compatible with the VESA adapter. The original article which I mentioned here:
http://docs.info.apple.com/article.html?artnum=302547
Basically says that. Only the 24 inch iMac and original iMac G5 have a VESA compatible mount.
Currently none exist that will do your machine, but
http://www.imacmount.com/ has announced they are working on mounts for other iMacs.