Will a physical copy of Fallout New Vegas work with Steam DlCs?

I'm getting this weird message saying that New Vegas wasn't installed on my windows 10 64bit notebook. I used Steam to successfully install the game to the default Steam folder on the C drive. However every time I try to run the game in Admin mode a weird message keeps telling me that New Vegas isn't... show more I'm getting this weird message saying that New Vegas wasn't installed on my windows 10 64bit notebook. I used Steam to successfully install the game to the default Steam folder on the C drive. However every time I try to run the game in Admin mode a weird message keeps telling me that New Vegas isn't installed and my computer cannot find the setup wizard to install it. I tried everything to fix this problem; even uninstalling and reinstalling Steam and moving the New Vegas files out of and back into the Steamapp folder on the C drive. I would like to know if I can just buy a cheap used NV PC disc from Ebay and have it work with my purchased digital Steam DLCs like Old World Blues and Honest Hearts.
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