Mmmm i need to develop 2 sites (diferent project).
The first project i need to use telerik version 2007.
in the second proyect i need to use the new version.
every project is for different customer.
But I need to have installed and develop in the same machine.
There is no issue with using different dll in different project. Issue comes only when you are trying to use different dll in one project. This is because the .NET framework does not allow you to use two different
versions of controls for
the same assembly in a single web-application since
the assembly names are the same, you cannot save both of these in the
same folder and also the namespaces are the same, which would not
allow you to use different assemblies on the same page or project. Thus,
if you want to use one version at a time and then upgrade it later in
the future, then you could save the dlls in different folders or
locations and refer to these as per requirement.