I recently rebuilt a dev machine and was trying to install .Net 1.1 and got the following error:
Error: internal error 2709 feature GUID for use by Cartman
It apparently happens when something goes wrong or you have an aborted installation of .Net 1.1 framework.
The fix for this can be downloaded from this address: http://astebner.sts.winisp.net/Tools/dotnetfx_cleanup_tool.zip
Just run the tool and it cleans up everything, my install then proceded flawlessly.
I found this fix on this post originally: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=9409&SiteID=1
Originally posted at http://geekswithblogs.net/rwillgoss/archive/2006/12/17/101385.aspx