Hello and happy new year

(a bit late, i know)
I have the following problem:
On an old box, I have PLOS 2007 installed. I attached a different monitor, with lower resolution (1280x1024). Before I did, i change the resolution and monitor type in the control center. Everything went fine. But!!!
Now I have the box attached to the old monitor (1900x1200), but cannot adjust the old monitor type (it's gone) and no other resolution than 1280x1024. I tried selecting plug and pray montor as type and it crashes immediately and my monitor says "signal out of range". I can change it to a generic 1900x1200 flat panel, but when i then adjust this resolution, it does not work (testing is black screen).
Please, could you help me get my monitor type and resoultions back?
Thanks in advance!
Peace
iFriend