F-Secure Virus Descriptions : 9999

There is no virus by this name, and there are no known common viruses that would activate on this date. However, some people are concerned that computers might go berzerk on this date, as some (typically, older) computer systems have used the "9999" symbol as an end-of-file marker.

This risk is probably not too big, and has nothing to do with viruses.

See: Y2K, http://www.F-Secure.com/v-descs/year2000.shtml