It sounds like you did the right thing, your old settings should be on your old pc at C:\users\USERNAME\My Documents\DonationCoder\ScreenshotCaptor\ScreenshotCaptor.ini.
Make sure on your new computer that you exit Screenshot Captor and then copy over the old files and then restart it.
Note: if you install the portable version of Screenshot Captor then you would put the files in the same directory as it.