A. No, it’s not a virus. Those green triangles are Excel’s way of telling you it believes the cells contain an error. Of course, sometimes Excel is wrong, but such error-flagging is a handy fail-safe function.
Why it happens: Excel 2002 and 2003 constantly work in the background scanning for possible errors. You can turn off the feature by clicking on Tools , Options and the Error Checking tab and unchecking the Enable background error checking . Then click on OK .