Windows 7 - Backup files fail to backup files in Program Files

The test result is under Windows 7 build 7000
1. Open backup and restore center
2. Set backup settings
a. Choose backup locations to local disk,for example f:\
b. Choose [Let me choose]
c. What do you want to back up?
Only choose the folder of c:\program files\windows photo viewer\
Do not choose [Include a system image]
d. Backup summary
Items are c:\program files\windows photo viewer\
e. Save settings and start backup

Result:
There is no files under F:\TEST-PC\Backup Set 2008-09-29 032022\Backup Files 2008-09-29 032022\Backup files 1.zip\

So, the question is why we can not backup this folder at the first time(it should be a full backup)

Anyone can help me, thank you in advance!

Hi

Backup doesn't usually back up a program's files. Since Programs need to be "Installed", it makes no sense to simply back up the program's "program files" folder if no User data is stored in such folders. Since that folder would be fully rebuilt upon it's reinstallation, why does a backup need to be made of it?
I tested this also, and while a backup file was created, the zip folder was empty as was yours.
But again, backing up such a folder makes no sense and is a waste of space in the backup file, so it only makes sense that certain file types are excluded from being backed up.

Thank you for your reply, and it seems system files are excluded from being backed up, so the next question is how did it distinguish which files are system files or user data?