QB 2006 - Must install on server where data file kept?

If you are truly in multi-user mode, with the data file on one computer being accessed from another computer then, of course the computer where the file is located must be 'on'. If you are trying to access any file, whatever the type, on another computer on your network, the computer where the file resides must be on. The only way you can access the file without both computers being on is to have two copies of the file, one on your computer and one on the other (off) computer. If that is what you are suggesting, then lots of luck. I can guarantee that, if you have two computers working on two different copies of the same company file those two copies will never look the same and will have irreconcilable differences.