I need computer help. Can you tell me what I am looking for on my computer? Details inside.

Last weekend, in an effort to free up some disk space I removed several files. I used the “Add/Remove Programs” file on the control panel screen. Evidently one of them that I removed is the one that allowed sound to come out of my computer and attached speakers.
Can I go back and find the removed files? Where do I look? Are they in the trashcan or something? What am I looking for exactly or what will it be called? I am still using Windows XP if that helps.