Hi. No, I've not made any changes to my PC. My anti-virus is McAfee, and I already know that I have to disable its real time scanning whilst unzipping the files else McAfee identifies some files as a virus. I have made sure that the files for this version have been unzipped properly.
I realise that I am using quite an old pc, and running Windows 7, and this is quite possibly the reason that I am having problems running this version of the game. But it still remains that I can run v0.5.1 fine on my pc, and versions v0.4 and v0.4.2 before it.