I have no idea why this is not actually an editor option built in, but still, nice to know it's *possible*.

I got this nice tip from a guy named Herfried K. Wagner (MVP)

 

"Once upon a time I asked if it was possible to display a vertical rule after 80 characters in the IDE's text editor.  Today I read the following suggestion in one of the public groups:

 

Note: Before touching your registry, make sure to back it up. Use this at your own risk!

 

Start RegEdit and open the following key:

 

'HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\7.1\Text Editor'

 

Create a new string named "Guides" and assign the value "RGB(128,0,0) 80".
This will display a vertical rule after 80 characters.  It's even possible to create more than one rule, for example "RGB(128,0,0) 95, 100".

 

This seems to work fine with VS 2003 and 2005 Beta 2!