.BUP File Extension

I have noticed several changes in my files. In my "Quarantine" folder, there is a huge collection of files with a .bup extension. There are also cryptic files in the Windows folder that didn't exist before. This includes duplicated folders that look like shortcuts, but they are not. Also, as an Administrator, I can't access these duplicated folders.

Any ideas? I am guessing that someone got into my system when I was using a wireless network, but now I am staying hard-wired behind my cable modem until I figure this out. I also found some text files that appear to have verbiage related to XHTML. Help!