Please dont ban me!

For asking suck a stupid question but could someone please show me how to do a if clause, like to make sure a users screen resolution is 800x600 or higher, I have already..

 System::Call 'user32::GetSystemMetrics(i 0) i .r0'
 System::Call 'user32::GetSystemMetrics(i 1) i .r1'
 !define CUR_HEIGHT $0
 !define CUR_WIDTH $1 

Take a look at IntCmp

IntCmp $0 800 OkLabel BadLabel OkLabel

BadLabel:

  MessageBox MB_OK "Get a bigger monitor, foo!"

  Abort

GoodLabel:

.

.

.