reducing mesh vertex count in blender

[Batman92]

Not sure if this is the correct forum..

 

All i want todo is reduce the amount of vertex's there are in a nif file using blender.

 

I have blender and plugin install and I can load the nif file correctly but when i try to add the modifier Decimate (vertex reducer) I get a "Modifiers cannot be applied to multi-user data".

 

I don't know blender but I can guess to what that error means but is there a work around for it.

 

I'm playing oblivion on a laptop and a lot of mod's work but will a lot of mod's cause to hectic slow down because of highly detailed meshes.