deleted files connected to operating system

I recently gave my ibook G4 to my Mom. I was trying to clean off all my personal information and I think I accidentally deleted files that the operating system,Tiger, OS X, needs to download files. I don't have the instillation disk that came with the laptop when I initially purchases it. If I went ahead and purchased Leopard would this resolve the downloads issue I am having? What do you think...

 

I can connect to the internet just fine. But say someone e-mails me a document. When the document downloads it will not open the document and if I try to open the document in word, and it is a word document and I have word on my computer, Its formatting is crazy. If I try to download an online player, it will not download any online players, and just bounces me back to the previous screen. Does not give an error message. The problem is solely with anything I try to download. I know I deleted a bunch of stuff from the computer. I am wondering if I accidentally deleted files from the computer that it needs to actually download information from the internet, and if so would installing leopard fix this problem. I did not have this problem before I deleted files from the computer.