Hi Glenn,

First, fixing a Windows XP, Vista or Windows 7 system that has errors due to a missing msvcr80.dll file is different from fixing errors due to a missing msvcr100.dll file. The msvcr80.dll file is part of the 2005 module of Microsoft Visual C++, while the msvcr100.dll file is for the 2010 module of Microsoft Visual C++...

These modules are integrated upon the installation of certain applications. This is in order for the developers of those software products to ensure that their applications can properly install and operate (the way that they intended to) in the user's system...

Second, check if you've accidentally deleted the msvcr80.dll file -- Do this by going to Recycle Bin to check if the file is still there. If so, restore it...

Otherwise, ttry the steps below if you're getting missing msvcr80.dll errors that are related to Apple iTunes...

*** IMPORTANT NOTE: If you're getting msvcr80.dll-related errors due to a different program (not Apple iTunes), then skip this part and move on to the last part of this post...

*** Take note that you may need to boot your system in safe mode in case you cannot properly access certain functions in your system due to these msvcr80.dll-related errors...

STEP 1. If any or all of the programs below are found in your Windows 7 desktop, then these should be uninstalled. Take note that you must uninstall these programs in the order as how they are listed below (first item should be uninstalled first, then the next and so on). When there are two versions of the same program in your computer, then you must uninstall the oldest version first...

Apple iTunes
Apple Software Update
Apple Mobile Device Support
Bonjour
Apple Application Support
iCloud
MobileMe

*** To uninstall these programs from your Windows 7 desktop, go to Control Panel, then to Programs & Features. Though uninstalling these programs won't touch your music collection, it'd be best to have your music collection backed up in a different partition or external data storage device before uninstalling these programs...

STEP 2. Reboot your computer. Check if the four folders below have been properly removed from your Windows 7 computer. Otherwise, delete them.
 
Bonjour -- This folder is normally found in the Program Files directory of local disk C...
Apple -- This folder is normally found in the Common Files folder under the Program Files directory of local disk C...
iPod -- This folder is normally found in the Program Files directory of local disk C...
iTunes -- This folder is normally found in the Program Files directory of local disk C...
 
STEP 3. Go to the Apple website and download the latest version of Apple iTunes for Windows 7. Execute the Apple iTunes installer that you downloaded by right-clicking on the file and selecting "Run as administrator"...
as an administrator. Usually this involves right-clicking on the installation program and choosing Run as administrator. That's it...

If your getting missing msvcr80.dll errors due to other programs (not Apple iTunes), or if the steps above don't work, then you can try the things below...

STEP 1. Go to http://www.microsoft.com/en-us/do... -- This is a page in the official Microsoft Download Center site for the Microsoft Visual C++ 2005 Service Pack 1 Redistributable Package MFC Security Update...

STEP 2. Choose the version (32-bit or 64-bit) of Microsoft Visual C++ 2005 Service Pack 1 Redistributable Package MFC Security Update and install it...

Hope this helps...