fizer icon (blue screened computer) appeared in my finder

fizer icon (blue screened computer) appeared in my finder. What is it and how do I get rid of it? Simultaneously numbered/lettered file names have appeared

Is it possible you have accidentally turned on "show hidden files?"

fizer has also appeared on my mac book pro

fizer has also appeared on my mac book pro. How do I delete it and if I have accidentally switched on show hidden files how do I check that.
Simultaneously some files in finder have started to be named with numbers and letters
My skype has inexplicably started to crash at startup too
Can anybody help?

could it be that this is just a Windows computer in your network and it's name is "fizer"? When you click on it in Finder, your computer tried to connect to it and the default symbol for a Windows machine on a Mac is a monitor with a blue screen.

To turn off, open the Finder preferences (menu bar: Finder -> Preferences) and deselect "Bonjour Computers" under "Shared". Voila!

mia,
I gave you a wild guess answer because you didn't give us enough info to really understand what is going on.
You need to elaborate what you see, where you see it, what OS X version(s), what you've done on both computers lately (updates, installs of software, etc). For example, I don't understand a "fizer icon."