Computer resolution problem

long long ago before i left my country i always fixed all the computers in the house. Whenever someone in my family ran into a problem with their computer i would surely fix it by the next day.

but now i have left my family, and they are without anyone to solve their computer problems. And as expected they called over to my new home where i live now, telling me that all the computers back at home have become sluggish, and were no longer working so well, For their wasnt another family member in the house that knew how to maintain a computer properly......

They are telling me through the phone that when they start up the computer the resolution ius very small (around 400x 600) and when they try to change it back to normal it won't set (they are limited to only one option). is there a problem with the graphics card, does anyone know a fix for this?

1 - be sure you have latest directx
1.5 - go to device manager, uninstall monitor and reboot, see if that fixes it.  if it says the wrong type of monitor is installed, manually select the right monitor through the Add New Hardware wizard.
2 - go to device manager or program files and see if there's a control program for your graphics card; try to reinstall graphics card drivers or update them.