Solution to the D7 "system. Pas not found" error

Sometimes some components will appear after being installed:
[Fatal error] project1.dpr (1): unit not found: 'System. pa' or binary equivalents (DCU, DPU)
I don't know why. At first, I had to reinstall Delphi to solve the problem. Later I checked the Borland official website and learned that it was only caused by the loss of the Environment library path. The solution is very simple, if you install the default path in D7, you only need to open the Delphi menu, select Tools> environment options, select the library tag, and add the following content in the library path:
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C: \ Program Files \ Borland \ Delphi7 \ Lib; C: \ Program Files \ Borland \ Delphi7 \ bin; C: \ Program Files \ Borland \ Delphi7 \ imports; C: \ Program Files \ Borland \ Delphi7 \ projects \ BPL; C: \ Program Files \ Borland \ Delphi7 \ rave5 \ Lib
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If it is not the default path, add your own paths.