how to access files on linux hard drive connected as external drive

[StariBrko]

main board on my computer gave its best.
hard drive is still working. i connected it as an external USB drive on Knoppix, and i was able to browse the content of the drive.
some directories, however, are not accessible due to insufficient access rights.
how can i reset file permissions in order to access files in those directories.

thanx for answers,
cheers