Another option is to save as and rename the fastener, with the assembly open, and place the newly named part from the toolbox and place it in your assembly folder, so it never looks at the C: or Network drive. The problem you are having has two roots, wrong configuration or wrong directory, i.e. cannot find part. I found it is nice to keep all the required parts in the same folder, which makes life a lot easier.
I had the same thing you mentioned happen to me at a design review, because I was using a different computer, and it took me a while to explain to everyone why my 1/4-20 SHCS was really 4X too big, not to mention embarrassing.