Judging from the title bar of the error message, it's about the DLL-File.
Something damaged or changed that file - either a virus (as the message suggested) or simply a failure during an access to it (for example, whenever windows crashes or the computer is switched off without shutdown, there is a chance of the file currenty being loaded to be damaged).
If nothing else reports errors, you can try searching for that DLL (it's part of several downloadable sample games) and replace it on your computer.
If replacing it doesn't help, or if it gets corrupted again shortly, then it's most probably a virus issue - the chance of a file being damaged by a crash is so low that it wouldn't create the same message by random...