I have both the Gog and retail copy of the Witcher. To save download time and usage, I installed the retail copy on my new Windows 8 laptop. I can't play it though because it says I have to sign in it as an Administrator.......even though I am the only profile on it and am the administrator. I done it in administrator mode and it still says i am unauthorized.

I haven't got Windows 8, but can you right click on the icon & go properties-security & edit the permissions?

I don`t know about Windows 8 but with windows 7 you need to update to the 1.5 patch and then remove the Tages drivers. The original Tages drivers were not compatible with 7 and going by that I would assume that they won`t be with 8 either. If you`re running the original red box game then you will also need to update to the 1.4 patch before updating to the 1.5. You can find the download links here.
http://en.thewitcher.com/the-witcher/1/updates/