We have ~10 users who run legacy (16-bit DOS on windows 98) data entry software against a Windows 2003 file server. Files are accessed directly (i.e. it runs as if it's a client application with network files constantly being accessed, not as a client/server app).
Lately, the performance of this application has been atrocious. 15 seconds to run a tiny report, or open up a new screen. But when we look at the server's performance metrics, there doesn't appear to be any problem. Low IOPS, no average disk wait, low read/write bytes, almost 0% CPU usage, tons of free RAM, etc. We've looked through every metric and seen nothing that seems even remotely close to the limits of the server.
We are in the process of replacing the software, but need to make it work for another year until our transition is complete. Any ideas on how we can determine the source of the issues?