As VS2008 can target the 2.0, 3.0, and 3.5 versions of the .NET Framework, IMO, there is no reason to even keep 2005 installed.

>As a side note, if someone is doing stuff using the 3.5 FW with VS2005, especially WPF, leave VS2005 behind forever and start using VS2008 now, your mental health will benefit from it.