"Acer.SCR" is a screensaver included with your Acer notebook. In most cases, the best solution is to either reinstall the screensaver or change it. On Windows XP, right-click the desktop and choose properties. Under the screensaver tab, you can either disable it or change it to a different one.
You can optionally contact Acer and let them know that their screensaver isn't working, or otherwise check if there's an update that corrects that issue.
In my opinion, screensavers aren't required for the notebook and can be disabled entirely - aside from slightly increased battery drain, the screen for LCDs is unlikely to receive screen-burn that normally affects desktops. A slightly better alternative is to use Power management (available in the Power button on the screensaver page) and turn the monitor off after 10-15 minutes.