external harddrive not visible on desktop

it is a new MacBookPro with Lion....I can see the external hard drive on the desktop (however I can see on the finder). What to do?
I am new to the forum. Thanks in advance for your help!
L.

Click on the Finder "preferences", click on the "general" tab. Place a check in the box that says "External disks" under the title "Show these items on the Desktop".

Thanks...and another question...

Thank you! It helped. Now I have a slightly different problem. In my previous mac when I used to lounge iPhoto or iTunes, the app would immediately connect to my external harddrive (which is where I keep my pics and music) and then show me all the files. In my new Mac iTunes and iPhoto are not automatically doing that (and I understand it should not), but how do I configure it in such a way that it does that?
Many thanks,

If I am understanding the problem correctly adding the hard drive to your login items should make the drive available for iTunes and iPhoto. Make sure the drive is connected and powered on. Then go into the Accounts preference pane and select "Login Items". Click the plus sign and add the drive to the login items.

This mounts the drive at every login whether you will be using those programs or not. I used to run an Automator workflow that I ran by double clicking it. The workflow attempted to connect with my library then launched iTunes. I used it with a Time Capsule but I bet a similar procedure would work with an external drive.

Thanks. All I want is that when I lounge iTunes or iPhoto that it looks for the library in my external harddrive. it is not doing that now. Most of the time I do not have the external hard drive connected to the mac. Only when I need to use iTunes or iPhoto and to search other files + time machine. In the suggestion you are giving me here, is that what will happen? I am not sure what you mean by "every log in", do you mean every log in of iTunes or iPhoto? is it the same as lounging? I may just be lost in translation here. Apologies.

By login I mean each time you start your user account. It would not matter what you are planning to do on the computer. If you only want to look for the drive when using iTunes or iPhoto don't add the drive to your login items. It sounds like you only want to look for the drive when you launch iTunes or iPhoto.

I can't test the Automator workflow at the moment to see if it could be modified to work with an external drive but I might be able to test it later today.

Great. Thanks! Whenever you can it'd be great.