What "re-adjustment" do you have in mind? For what country is this application?
In the industrialised world, those who run 800x600 do so often because of weak eyesight, so shrinking the lot to fit has no purpose. 640x480 is prehistoric. "Etc" is undefined - what does it mean? Resizing controls to accommodate everyything on a smaller-resolution screen would require changing font and make the font sizes out of whack with all other text the user is used to on the user's specific screen.
Very old office equipment runs 4:3 (1024 x 768), less old on LCD 1280x1024, newer 1650x1050, netbooks 1024x600 ... you have much less real estate to manage than in 1920x1080.
I check who the users are , and then design to the resolution that fits most, so they do not need to scroll either vertically or horizontally. Those with lesser resolutions then have to scroll, those with higher resolutions will still have space on their screens.
For vertical resolution, other than redesign of your form (and next time, start off with the most likely resolution), you have the option of adding a page mark to the form , and some GotoPage buttons, so that only part of the form is displayed at one time. AS to what the screen resolution is, there is some WIndows API that can return the screen size. Google. There was also a post on something similar here on AWF earlier this year - try restricting google to awf.