You all are right, but I did do a spyware / virus removal like she requested after she said she would give me the money first of the month. She agreed to pay for this when we discussed ordering everything.
What do you normally charge for that? Labor by the hour? Add that to the $25 and you're good!
Verbal agreements are always dicey. That being said, the only leverage you have is to refuse to return the PC unless she pays you for the additional service. This sucks all the way around in the end. You just have to decide which is more important: the money with a possible bad review from her or cut your losses and suffer no negative review.