Awhile back, I imported a C++Builder 4 project into XE5, and it's been working just fine for years. But yesterday, I tried to open C++Builder 4 for fun (it didn't open), but now my project in XE5 says unable to open file vcl40.lib.
I need to stress, the project is in its own new directory where I've been building it for years. But I think because I tried to open BCB4, it changed something, maybe in the registry? And now, when I build this program with XE5, it has this hiccup.
BTW, I was unable to open the old BCB4 because a message came up that the program couldn't find vcl40, if that's any help.
Edit: By now it seems likely that your OS installation is damaged.
Perform a clean installation of XE5 (plus any custom extensions) on a clean Windows OS on a new computer.