>Hi,
>
>The machine running the system are fine, they are brand new.
>I don't use extensive graphics or resources at all.
>
>The battery of the system are okay. My application just keep
>waiting for certain file, on detecting them, will unzip and
>post all the file into their respective files. That all.
>
>I using only Win32 API sleep and doevent() only.
>
>It just give me problem of the system time slow down by
>half any hours or more.
>
Why not just re-engineer this to do away with the Win32 component? A form with a timer that performed the poll could substitute for the Sleep() API call, and would eliminate that as a source of the time loss. You simply start the form and sit at a READ EVENTS to run the form; it provides you with an easy shutdown point as well if you put such in the Form. This eliminates any suspecicion that Sleep() is behind the loss of time.

If you suspect VFP is the source of the time loss, you could also do the polling in a language other than VFP - it'd be fairly simple to write in VBScript, for example, and just trigger the VFP app when there's work to be done. By not having the VFP app running constantly, you eliminate any suspicion that VFP is causing the time loss.

The illegal operation error after just sitting for extended periods of time would tend to make me suspect the platform the app ran on. It's unusual to see things just die at random after sitting idle for long periods of time.