This will result in incorrect calibration as the loading screen is at a reduced resolution (800 x 600 or something). Something I've seen happening quite commonly is monitors on first use decide to auto calibrate when Windows is on the loading screen.
This should be done once the system is fully booted up and logged in, and the resolution and refresh rate is set properly. This calibrates and synchronises the monitor with the VGA output from your computer. Next I would generally auto tune the monitor - there is usually a button on the monitor itself labelled Auto, Auto Setup, or something along those lines. The refresh rate will be in advanced settings. This will in your desktop settings menu (right click on desktop - screen resolution). If it's not, the monitor will attempt to scale the output to fit, and it won't look crisp. First you want to make sure the output from your computer is at the monitors native resolution (1366 x 768, 60 hz).