emelfm2 or midnight commander

They are great file system managers! I use emelfm2, so I'll show you how using that...

Start xterm
make sure you have a root program, like rootsh or gainroot
become root (by typing "root" or "sudo gainroot" or whatever)
type emelfm2 and press enter
Then browse to /usr/lib (its just like in windows explorer)
ta da!!!

I am not sure if these programs are available for N900, this is for N8x0.

You can always access this from the command line and use mv to move files.