Problems with screen resolution...?

I just got windows xp reinstalled on my comp and hooked it up to my monitor (used a diffeferent one for the installation though) a 22 inch Dell LCD. However, the computer doesn't recognize it and can only display some crappy resolution makes stuff look too big. It just says default monitor (in properties, guess it doesn't recognize it?) and I can't even see or change the refresh rate. And when I try for the maximum resolution it says ';cannot display this video mode'; which never happened before and says optimum resolution 1680 x 1050 or something (I don't have that option only 1680 x 1200 and one above it which render the same result). Now I tried this comp on my other LCD monitor which is identical and was running with another Compaq comp whose resolution was fine, nothing happened. After I hooked my old Compaq back in and after I shut it down and reopened it I got bad resolution on this one too and I got the same message, when I tried to change it (max was 1680 x 1200). The resolution was fine before and it was at the optimum for the screen and now it's all messed up (well everything's to big). I tried going into safe mode on the Compaq and set the resolution higher (it went up higher 17xx x 19xx or something) anyway when I shut down and opened the computer normally it had the 1680 x 1050 option available again but when I shut down/opened it again it went back to the same crappy one and it seems the resolution only stays like this until you shut it down. Dell had something on their webpage about powering off monitors and starting them again but that doesn't do anything... Anyone know how I can change my resolution so it's not all crunched up? The safe mode thing doesn't work for the other comp though, only the compaq.Problems with screen resolution...?
Have you downloaded the drivers for your video card?