1. Close Visual Studio if already open
2. Open regedit
3. Go to [HKEY_CURRENT_USER]\Software\Microsoft\VisualStudio\8.0\Text Editor
4. Create a new string value and call it 'Guides'
5. Set the guides by specifying an RGB color and the location of the lines. for example:
Guides = RGB(224,224,224) 4, 8, 12, 16, 20
The above will give you lightly colored grey lines. You can change this to whatever you prefer by adjusting the RGB values contained in the brackets.
6. Open VS2005 and you will see the lines.