how to ShowAllFiles in terminal for "lost found" file

hi all,

i am trying to verify that i can delete two iNode files of 5 GB each on a mac air and i am not sure how to enter the commands in terminal correctly to view the files before deleting each of these.

for instance i am entering:

defaults write com.apple.finder AppleShowAllFiles

and then hitting ENTER and i get the response "could not write to domain Users/....Preferences/com.apple.finder; exiting"

is this due to being out of disk space?

i have run out of disk space so i /have/ been getting various error messages about apps not being able to sync to my DROPBOX folder as the drive is out of space however i took a large amount of information off dropbox (onto my desktop) so i am a little curious as to why i am getting this error.

anyways, deleting these two files would help a lot.

THANKS