help with deleting a file

Hi, sorry i am not a tech person. I love portable apps.
I am using portable firefox. The latest RC3. Yesterday i took my USB home and got a strange message...
file corrupt firefox/data/profile/prefs/js

That should be backslashes but i cannot find the key.
I have tried to remove and reinstall the program but it will not let me remove the file....
please help me...

thanks
adam