Likely you have set your folders/files to "show hidden files."
Word creates temporary files that are hidden from normal view, and sometimes they do not get cleared out when you exit your document, and are left behind on the disk. These files do pop up when you save or have the program set to save a document in progress.
Scan these ~$$ files with your virus scanner program if you think it necessary.
Nothing to worry about.
I have an HP Pavilion dv6 with Windows 7 Home Premium and a 64-bit OS. The version of Word I'm using is Microsoft Word Starter.
For some reason whenever I save a .docx file from microsoft word it will create both a usable file and a strange unusable file with the first two letters of the file name replaced with ~$.
If I try to open one of these files an alert pops up saying the file cannot be opened because of problems with it's contents.
If I show the details it just tells my that the file is corrupt and cannot be opened.
I don't know if this is from a virus or if there's something wrong with my version of word but it's very strange and a bit disturbing.