Solved: MS Money Backup

This may be a software question vs. Win 7, I'm not sure.
One of the options of MS Money is "backup upon exit".
I chose this and it backs up fine upon exit.
But there's a flaw (I think).
I back up to hard drive. It works fine.
Once in a awhile, I'll back up to external hard drive. That also works fine.
However, once you back up to external, this changes the default backup location. When I try to go back to automatically backing up to hard drive (in the same location I previously used), it will say "file is read only" - "choose a different file name".
I know how to change file from read only. I'm just wondering why or how Money is using a Read Only file to back up. Is this normal or is money or windows somehow changing a file to read only?

Thanks