Charging customers for software you need to fix their problem.

I am a relativly small-time (50 customers) trainer of people needing help with their computers. I deal primarily with senior citizens but also offer my services to small to medium-sized businesses.
I have found several customers lately that have made the mistake of falling for the phoney trojan warnings found at some web sites and even buying the software when redirected.
There are several programs available to clean up the mess, but not being able to get on the internet in some cases, I need to bring my own to make the fix.

Question: Do I charge the customer for the software that I may need to buy to fix their particular problem?

Thanks for any input.

-Terry