>Is your user doing his work on a PC with local data?
Or is it a PC connected to a server?

Ok. I tell you.

My client has 3 machines. One is the server and he works on it. There he works all the time. He sells, he charge his movements and there's no problem.

3 days a week an employee uses a second machine and charges more movements and changes prices. What you can call "paperwork"

Most of work is the same her employer does on server every day without problems.

About one time a week she has "read error" on server's hard disk or server's removable disk (I insist working on server there's no problem) and that was with wired net and now with wireless net.

The third machine is almost turned off all the time and when is turned on it doesn't work... Don't ask me why technician always has to reinstall Windows.

I'm apologize for annoying you by mail. Do you think antivirus can cause this kind of problem?

Thank you.

Héctor