Some computer woes...

I am blogging from Sebastian's computer now. I tried to update my Norton Internet Security package. All went fine until it was time to install. I must first delete all previous Norton files and applications - tried to do that, but apparantly there are at least two files that were damaged at some point, and I cannot seem to delete them - they won't leave. What should I do? Give me some advice. There is also still a file called Norton Internet Security under "programs", but if I try to delete, the computer says deleting could negatively effect other programs on the computer. Is this accurate? Sorry I am blogging so fast, but I have to leave in four minutes for an appointment and will be back this evening (German time). Vielen Dank für die Hilfe.