OK, so I bought my PS3 on Boxing Day, and under Videos it showed my laptop so I opened it and it said not allowed. So I went into Media Streaming options on my laptop and allowed every device of the network (There were about 3 unknown devices on there!). Then I could access it but only the sample Landscapes video in the Public Videos folder, So I went into Windows Media Player and added the Movies folder on my external harddrive (which was plugged in) and the Video's folder in my account. I also changed the name to 'Xcellerator Mainframe' for fun!
Here are the settings I have done:

and

