Jay's username ends in 88, presumably the year he was born, as this was popular at the time. This would have made him 11 years old, considering the movie was set in 1999.
In the very beginning with the screen of the computer booting up, it says that the BIOS date is 09/29/91, but then further down it says "Auto-detecting USB Mass Storage Devices," but USB didn't become a standard until 1996 and a BIOS from 1991 certainly wouldn't have been able to detect them. It also says USB 2.0 which didn't come out until 2000.