My antivirus software has detected two threats, and I was wondering if either were serious.? Options

[lisasctt4]

To preface, I use AVG, although, not the free version. The threats it has detected are roughly the same, with the object name differing by one letter, and are as follows:

Object name: C:\hp\drivers\printers\photosmart\cdrom \DigitImg\instmsiw.exe
Detection name: The file is signed with a broken digital signature, issued by: Microsoft Corporation.
Object type: File
SDK type: Core

Object name: C:\hp\drivers\printers\photosmart\cdrom \DigitImg\instmsia.exe
Detection name: The file is signed with a broken digital signature, issued by: Microsoft Corporation.
Object type: File
SDK type: Core

AVG has a section under SDK type for "Result" and "Action History," but for both detected files, they are blank.

Are these files a problem? Are they serious? Any help is greatly appreciated. Thanks.