I uninstalled Apple Software Update in my Boot Camp Windows 7 install as it was crashing every launch, and a repair of Apple Software Update through Programs and Features didn't fix the problem.
However, re-running Boot Camp Tools' setup.exe (it gives me a choice to do a repair) does not reinstall the Apple Software Update it initially installed.
I suppose you could be in the same situation if you chose not to use Software Update when prompted during the Boot Camp Tools install.
How do I install the Apple Software Update associated with Boot Camp when Boot Camp is already installed?