Gateway 450SX4 Laptop Can't turn on

Hello,
The last time I used this computer, it functioned fine. It has been unused for a few months and I tried to boot it up recently but with no success. It opens with the Gateway screen and lights flashing, clicks, then goes to black but lighted screen. I have been able to get it to show the dos screen but can do nothing with that. The black screen has a bar /dash at the top left flashing but nothing else. All of the keys when pressed sound a bell. Any ideas and if so what can I do to fix the problem?