were you taking the (exe.) of the file from C:/Program Files/ ? if you were taking the files from here there is your problem right there NEVER unless you REALLY know what you are doing touch the files in your (C: ) drive
If your were taking the files from your (C: ) than there is no other way to fix your problem that feesing up to your father tell him what you have done his computer it will need to be taken to an IT expert and his computer will need to be completely cleared of what ever is on it and then a clean copy of windows will have to be put back on for operation!
I had a much longer post here, but I decided to summarize it.
This is the most inept, niave, and presumptious post I have ever read. Also, honestly I'm not sure why the IT experts computer would need to be completely cleared. But I guess that's why we're not IT experts.