According to the forum:
"The Witcher protection system does not support any kind of emulation software such as e.g. CloneCD or DaemonTools. Using it may result in non-detecting a dvd with the game. Also try downloading drivers for Tages from
http://www.tagesprotection.com/5.5.htm Unistall older drivers, start The Witcher and allow Tages to install newer ones."
If you have DT or similar, remove it and try.
I Don't see people complaining with loading or install problems. Point me the forum thread so I can help you.