According to this link, some third party "helper/cleaner" programs can disable Microsoft Help and Support.
"Have you ever used any third party applications on your system where the product description includes such descriptive phrases as:
cleaner, mechanic, detective, cure, optimize, clean up, tune up, speed up, fix up, compact, compress, faster, power, boost, booster, guaranteed.
The Help and Support Center sometimes get broken with overzealous cleaning and there are lots of things to "try" that sometimes work and sometimes they don't. Sometimes people just give up and never use Help and Support Center again, but it can always be repaired."
You can download the Windows 7 Help and Support program here.