Wat i feel is that if u save a copy of ur project somewhere else then changing the original will not at all affect the copy. Are u using VB6?
You need to keep in mind that a VB "project" is more than one file. (Keep in mind I'm also talking about VB6 - not really familiar with .Net or 2005 version/s). Each form, module, class etc is a separate file. To make a useful backup copy you would need to copy the entire folder. I usually do so by zipping the folder.