[XFree86] I must have messed something up

[Nino McFarland]

I was changing the moniter on my mandrake system because I only could get a resolution of 800 X 600 and I know I can get a wanted resolution of 1024 X 768.  I changed the moniter and resolution and my screen blacked out and I don't know how to view my desktop again.  The moniter just says "Out of Range".  I was wondering if you could tell me what should I do, in both cases. Thanks in aadvance.   Donald