Cannot download iTunes 7 and trouble with existing iTunes file

Question

I downloaded iTunes onto my hard drive on my computer but also onto an external hard drive as well. Everything worked fine until I went to open iTunes on my desktop one day and an error window popped up.
"Windows - No Disk
Exception Processing Message c0000013 Parameters 75b6bf9c 4 75b6bf9c 75b6bf9c"
With buttons Cancel, Try Again & Continue.
If I close the warning windows (2 always pop up) I get an iTunes Setup Assistant window.
"Warning!
iTunes was not properly installed. If you want iTunes to be able to retrieve CD information from the internet, you need to reinstall iTunes."
When I press the "Okay" button on that window, iTunes opens without a problem and with all the music in my iTunes library. I've been able to use it just fine with my iPod and on the iTunes store.
However, I have attempted to download iTunes 7 and it has not let me. I have successfully downloaded the iTunes 7 Set-up file. When I go to run the file, it wants to put the iTunes in my J: drive. The J: drive isn't on my computer though because it says it has 0KB space available on the drive. When I try and change the destination of iTunes it says "The volume J: is currently unavailable. Please select another." It won't let me select another and then immediatly takes me to the last page of the installer where it says:
"The installer encountered errors before it could be completed..."
Enpower (?) Desktop   Windows XP  
Enpower (?) Desktop   Windows XP  
Enpower (?) Desktop   Windows XP  

Answer 1

okay. i've seen four or five of these lately. it
seems to be associated with something to do with
external drives and/or drive letter assignments, and
can hit other programs than itunes (according to a
thread i found at the Microsoft Newsgroups).
here's a search on the error code here at
Discussions:
c0000013
... are any of the links in the various threads there
of any assistance with your manifestation of this?
Make that six. I am now receiving the exact same error message. My message makes iTunes completely inoperable and there is no way for me to get around it. Yes, I too have external drives attached to my computer. Anyone have advice on how to deal with this exception errort? I hope Apple has fix for us soon.
Thanks in advance for any help!