Please don’t use such non-descript titles.
Which version, which OS etc.?
Have you ever had a version of Photoshop installed and if so, have you uninstalled or just deleted the program?
Have you tried running the clean script?
Glad that you got it fixed.
If you do not mind, please post how your friend fixed things, as that might help others in the future.
Also, most users do not experience installation errors, so most of us only know things that we have read about, that fixed installation problems.
Thanks in advance, and good luck,
Europe, Middle East and Africa