Laptop monitor replacement question

I've had an Inspiron 9100 with the WUXGA screen for 4 and a half years now and it's still holding up strong... until I dropped it and broke the screen. I'm looking for a replacement and am wondering if I can buy a WXGA screen (it's cheaper) and have it still work with the system I have. I don't care about the resolution since I use an giant external monitor as my primary screen, but I do need the laptop screen to work in case I ever need to reinstall windows... my external monitor doesn't seem to work until the driver kicks in in windows (unless someone can save me $80-$100 and explain how I can set it to show the booting, etc. on the external) and reinstalling windows without a monitor is pretty much impossible.

Thanks for the help in advance...

 

If you disconnect the broken monitor internally and connect an external unit, the laptop should default to the external monitor at BIOS. I'm pretty sure there are other ways to do this, but I think this is the most sure-fire way.

 

Yeah I tried that, the broken screen is actually sitting in a drawer somewhere and the "monitor" that windows thinks is still there is disabled in device manager... but it still doesn't show the bios on my monitor, and doesn't show anything until windows loads. Frustrating...