Windows 7: Some programs on start menu showing the "unknown" icon

For some reason, Adobe Acrobat Pro, PowerPoint, and QuickTime all have the default Windows "unknown" icon next to them on my Start Menu (and also on the taskbar if I open the program.) I thought I might be able to right click -> Properties -> "Change Icon" but it is greyed out and I can't even click on the "Change Icon" button.

Anyone know how I can fix this?

Hi,
Take a look at this post.

Generic icons

This fixed it! Thank you!!

Here are the instructions from pbcopter's link in case others have this problem:

• Delete the file IconCache.db in C:\Users\yourname\AppData\Local
• Create a new empty file named IconCache.db in the same folder. This can be done, for example, by opening Notepad and doing nothing but going to save, entering the aforementioned file name exactly as written, and clicking save.
• Right click the file you have just created and make it Read Only. Vital step!!
  
• Reboot the computer. All your icons are recreated correctly.
• Go to the IconCache.db file you created and uncheck the Read Only box.