Dual Monitor Question

[gonores]

While sitting around at my parents' house between moves, I decided to see what I could do in terms of a dual monitor setup on my laptop. I took my desktop's monitor (21.3" Samsung LCD) and plugged it in to my laptop via the VGA outlet. My laptop does not have a DVI outlet, but my monitor is DVI capable. After dinking around a little bit with the graphics settings, I finally got the extended desktop option set up, and it appears to be working fine except for one issue...the external 2nd monitor flashes its portion of the desktop for like half a second, then goes black for like 2 seconds, then flashes again, goes black again, etc.

I'm not too technologically savvy, and the few things I've tried have not worked. Any ideas?

Thanks in Advance

Doug