%APPDATA% is just a pointer to the application data folder of the currently logged in user on the drive Windows is installed on (which will always be on your C: drive for a standard Windows installation). The folder you're actually looking for is F:\Users\USERNAME\Appdata\Roaming\Bitcoin\ where USERNAME is your user name on your original Windows installation. Copy the wallet.dat file from that folder to %APPDATA%\Bitcoin\ (overwriting the wallet that's already there, assuming you haven't already tried to receive coins with it - make backups of everything if you're unsure) and everything should be good.
Thanks for this reply, yeah it completely worked, I just had to access the drive I was exploring and then find the user file, I think I was put off that this was the place because it takes a long time to access (permissions etc). If you're willing to reply, do you have any idea how to actually withdraw funds from Mt Gox? I've tried e-mailing them but I can't make sense of a word they say - without wanting to sound like a dick I think it's a bit of a language barrier issue. I tried Bank Transfer but it just keeps rejecting saying they wont trade GBP (even though I requested EUR).