Thanks David, that really help...
One more question...I have a disk/device called shm mounted under /dev that is 251 Mb but completely empty. What is that?
Filesystem Size Used Avail Use% Mounted on
/dev/hda5 8.6G 2.7G 5.5G 33% /
/dev/hda3 99M 14M 80M 15% /boot
none 251M 0 251M 0% /dev/shm <-----This one