I have an Acer Aspire One MiniBook. I once had it

I have an Acer Aspire One MiniBook. I once had it hooked up to another VGA monitor. Now when I log in it shows the ACER logo and the XP screen then turns black. i can hear the windows start up sound and when i reset it i hear the shutdown sound but cant get the desktop to show up. When i hook it up VGA to another monitor it does the same thing on the other monitor and wont switch back. I have tried SAFE MODE but it gets stuck in the dos looking mode. Please help.