Okay Lots of users don't know the setup issues. Like for example if you download any setup like MSN,Yahoo. Some time when you double click for installation Its not open. After clicking it A black screen (DOS) open and disappears. What is this ? Is this because your system infected with virus ? No This is because downloading is not complete or some error inside that program. I mean no worried about it. Just re-download again and install. Thats easy.

I know. But I tell you that last time when my system in infected with virus. It damage my rar,zip files and also setup files. Its doing the same as you told a DOS type window. So in my view its happen also if your pc infected with viruses.