cannot delete files

hello,
can you post some information?

What files are you trying to delete? In general, if you can't delete them you are not supposed to. Ubuntu (and Linux in general) have a different approach than windows. You can make any change you want to your "home" folder and all it's contents but that is it. You are not supposed to delete or change system files as that is a surefire way to mess up the system.

That said, if you need to change or modify the system and you have a good reason to do so, then you will need to become root. Root is the equivalent of an admin and has ultimate power. In Ubuntu, you become root by using the sudo command. So, if you want to delete a file in /etc you would do

sudo rm /etc/foo.bar

That will remove the file. There are a lot of ways to use the rm command to do more than just remove one file but it's a fairly dangerous command for the novice and expert alike so best to not go around removing system files. For more on sudo see https://help.ubuntu.com/community/RootSudo

i was deleting files on my pendrive not a system file

Try

gksudo nautilus

in a terminal. Navigate to your flash drive and delete the files. Be sure to empty the trash before removing the flash drive or they are still there. Also be careful running Nautilus with root privileges as you can easily mess stuff up if you aren't careful.

You can also use the rm command above but you will need the full path to the files.

how do i navigate to the flash drive

hello,
some pendrive have a lock on it..maybe your pendrive have 'lock'..if so,open the lock.

thank you

delete my files