I installed ubuntu on an old Dell Latitude D630 laptop from a USB stick. I had an external monitor hooked in at the time, and during the installation, ubuntu found my external monitor without a problem. And I continued to install ubuntu.
Great... now, I started using my installed ubuntu, but I didn't restart my computer. I had setup my external monitor so that instead of mirroring my laptop display, it was an extension. Everything so far was fine.
Then as some point, my external monitor went blank. I had to power cycle my laptop. On the first power cycle, I saw what looked like 'frozen white noise' on both displays. I also noticed that my ubuntu install-usb stick was still inserted into my laptop. So, I pulled that out and restarted. This time, my laptop booted up properly, but I lost my external monitor use. When I try to detect the monitor, it never appears.
Could anyone help me get my monitor back on line? Here's the thing, I went back to the installation process found on my usb stick. The installation program can find the external monitor fine. So I don't know what is going on here.