It is no longer a common requirement on Windows 7 or later operating systems to manually calibrate the monitor for IRRICAD by specifying the vertical or horizontal correction in the VCADD.ini. If the circles or circular cursor do not display perfectly round check you are using the optimal resolution in Control Panel | Display. If you have been able to optimise the resolution change the VCADD.ini file back to the default settings:
[VCDefaults]
HorzCorr = 1
VertCorr = 1