Depends on what you were trying to do and where it is.
First, is the disk your system drive, another drive on your PC, or a shared network drive? Sounds like it is on a shared system but this is a guess on my part. It is possible using Windows Workgroups (rather than domains) to allow other users to share a database on your local system, and you didn't specify your environment in your question.
I am inferring from the fact that you asked the question in the first place that you don't understand the problem too well. That error is a warning that something is wrong with the disk. Unless the disk is question is a removable drive with a physical write-lock tab, you have a hardware problem with that disk. If it is a non-removable disk, it is dying on you.
If it is your system drive or another local drive, get help immediately to back up what you can. If it is a network drive, talk to the network admin or the system admin for the server that serves the DB. THAT person will be doing a backup real quick.
Eventually, someone will have to run a diagnostic program to see if the disk controller or disk surface is, in highly technical terms, hosed to tears.
If so, a good backup is going to save someone's life. A bad one will probably cause so much stress as to prematurely end it.