Is this dBase 5.0 for DOS or a later version? There are applications being run for the 5.0 DOS version run on many versions of Windows including 98, 98se, Me, 2000, and XP. Yes, on the NT family (2000 and XP) there are certain weird issues that pop up but you just have to program around them.
One undocumented surprise in NT-family versions like 2000 and XP that I haven't seen mentioned elsewhere is that in a multiuser networked environment if you're in a SCAN/ENDSCAN loop and fail to open a table or record because another user has it open, the SCAN loop can abort prematurely without any warning after the standard "File is in Use" error. If another user has the record locked, we can try LOCKing the record first and avoid corrupting the SCAN looping environment, but there is no similar command to detect whether the table is in use. (Hmm, I know I tested USE but did I ever try low-level access using the FOPEN function? Can't remember now. Still, that would be a rather extreme workaround.) Ouch, in some critical code I had to resort to DO WHILE/SKIP/ENDDO.
While your problem as described does not sound familiar, I wonder if what your're really seeing is the effects of running the dBase program in a Cmd.exe DOS-box rather than using Command.com. Set one of the available properties of Command.com on the Misc tab, Idle Sensistivity, from the centerpoint toward the right side of the scale. By using Command.com and changing that Idle Sensistivity setting, Windows programs will open faster when the dBase application is running and, conversely, in dBase the keyboard will respond faster without delays where you can count a second between each keystroke appearing on an entry field.
Cmd.exe is easily available from the Start, All Programs, Accessories, Command Prompt. It is the most powerful for command line interface (CLI) with the XP system, and you can try fiddling with the Compatibility tab in its properties, but older 16-bit programs such as dBase 5.0 probably will do better with Command.com. Simple just to create a shortcut for it, right-click on the desktop and select create shortcut. In XP systems, Command.com is in C:\Windows\System32Command.com.