I had no problem installing it before
I wanted play again so i got to install about 30~40% in it ask for assets1.pk3 file on disk2
I brows and point to where it is(gamedata\base) but it says it's not there and ask me to insert cd2...
there is no problem with cd2, I can read it fine

I'm not sure what you are saying, but if I were to guess I think you mean you are directly going to assets1.pk3. When it asks for disk2 containing assets1.pk3, just put in disk2 and click OK.

perhaps you could try just leaving it at the drive letter instead of navigating the whole way to the file?

I'm not sure what you are saying, but if I were to guess I think you mean you are directly going to assets1.pk3. When it asks for disk2 containing assets1.pk3, just put in disk2 and click OK.

yes, it asks to locate assets1.pk3 file so.. I insert disk2 and click ok
it still asks, it says assets1.pk3 file is not there
I tried copying assets1.pk3 file to else where, even directly into JKA folder, still doesn't work

You probably have a defective disk. (from being scratched.) I had a problem simular with Jedi Outcast. All you can really do is buy a new copy of Jedi Academy.